Chapter 12. Biology and Diseases of Dogs Flashcards
1
Q
Dog taxonomy
A
Order Carnivora
Suborder Caniformia
Superfamily Canoidea
Family Canidae
Domestic dog = subsp. Canis lupus familiaris
-Domestic dog may have descended from prehistoric canids in Europe ~ 18,000-32,000 years ago; East Asian origin also possible
2
Q
Other members of genus Canis
A
4 species of jackal and coyote (C. latrans)
3
Q
William Harvey
A
Used dogs to study cardiac movement
4
Q
Marcello Malpighi
A
Used dogs to study basic lung anatomy & function
5
Q
Sir Christopher Wren
A
Used dogs to demonstrate feasibility or IV delivery or medications
6
Q
Banting & Best
A
Used dogs to identify the role of insulin in diabetes
7
Q
Dog breed most commonly bred for use in biomedical research
A
Beagle
8
Q
Spontaneous conditions studied in dogs
A
- Grey collie colony: cyclic hematopoiesis = periodic fluctuations of the cellular components of the blood, esp neutrophils
- Golden retrievers: Duchenne muscular dystrophy = absence of muscle protein dystrophin, inherited in an X-linked recessive manner
- Doberman pinscher: Hereditary canine spinal muscle atrophy & Narcolepsy
- Bedlington terrier: copper storage diseases (such as Wison’s disease)
- Spontaneous diabetes mellitus and hypothyroidism
9
Q
Conditioned dogs
A
Random source dogs that have been treated and vaccinated in preparation for use in research
-These dogs are then suitable for long-term studies
10
Q
Non-conditioned random source dogs
A
Useful only in a limited number of research studies, such as nonsurvival surgical training & tissue/organ harvest
11
Q
Class A licensed dealers
A
Raise all animals on their premises from a closed colony
12
Q
Class B licensed dealers
A
Purchase the dogs from other individuals (including unadopted dogs from municipal pounds) & resell to research facilities
13
Q
NIH NOT-OD-14-032 Notice regarding NIH plan to transition from use of USDA Class B dogs to other legal sources
A
- Began in fiscal year 2015
- Prohibits procurement of dogs from Class B dealers using NIH grant funds
14
Q
Federal regulations promulgated by APHIS, USDA in response to the AWA (7 CFR 2.17, 2.51, 371.5)
A
Described in 9 CFR Chapter 1, Subchapter A, Animal Welfare
-Information on care and use of dogs in research: Subpart A, Specifications for the Humane Handling, Care, Treatment, Transportation of Dogs and Cats of Part 3 (Standards) to Subchapter A
15
Q
8th edition of The Guide
A
“Enclosures that allow greater freedom of movement and unrestricted height (i.e. pens, runs, or kennels) are preferable”
16
Q
Dog normal vital signs
A
- Temp: 37.9-39.9 C (100.2-103.8 F)
- HR: 70-120 bpm
- RR: 18-34 bpm
- CRT <2 sec
17
Q
Leading provider of nutrient recommendations for dogs?
A
NRC of the United State National Academy of Sciences
18
Q
NRC publications form the basis for what dog nutrient profiles?
A
Association of American Feed Control Officials (AAFCO)
- AAFCO is an advisory body comprising state representatives
- Provides a mechanism for developing and implementing uniform and equitable laws, regulations, standards, and enforcement polices & establishes nutrient profiles for cat and dog foods
19
Q
Maintenance energy requirement (MER)
A
- The amount of energy used by a moderately active adult animal in a thermoneutral environment
- MER = BW x 0.75 x 550 kJ DE (digestible energy)
20
Q
Open formula diets
A
- Have defined concentrations of all ingredients and the information is publicly available
- Occasionally may require changes in formulation to maintain nutrient composition or meet changing nutrient requirements - changes are made public
21
Q
Closed formula diets
A
- Commercially available, balanced diets that meet and label the minimum requirements for protein & fat, and maximum values for ash & fiber
- Exact composition of ingredients may vary from batch to batch based on a least cost strategy
- Types of closed diets include ‘fixed formula’, ‘constant nutrition’
22
Q
Fixed formula diets
A
- Type of closed diet
- Quantitative ingredient formulation does not changes
- However, this information is proprietary & not disclosed publically
23
Q
Semi-purified & purified diets
A
- Provide strictest control of ingredients
- Formulated from purified components: amino acid, lipids, carbohydrates, vitamins, minerals
- Generally open formulas
24
Q
As a general rule, diets are safe for consumption for how long after the manufacture date?
A
6 months (when stored at room temp; refrigeration may prolong)
25
Age range for best conception rates in beagles
- 2 to 3.5 years old
- Also have best litter size with the lowest neonatal mortality
- After 5 years of age, conception rates and litter size decline & neonatal mortality increases
26
Female reproductive anatomy of the dog
- Deep ventral clitoral fossa in vagina
- Uterus consists of cervix, uterine body, and uterine horns
- Cervix is an abdominal organ, located ~halfway between ovaries and vulva; cervix is enlarged and turgid during proestrus and estrus
27
Estrous cycle in dogs
- Monoestrous, typically nonseasonal spontaneous ovulators
- Have a spontaneous luteal phase ~5 days longer than the days of pregnancy followed by obligate anestrus
- Proestrus lasts 5-20 days (avg 9) - serosanguinous vaginal discharge; follicular phase increase in estrogen
- Estrus lasts 5-15 days (avg 9); first abrupt increase in progesterone (>5 ng/mL) + LH surge - ovulation follows within 24-72 hr; vulva softer and smaller than in proestrus; serosanguinous or straw colored vaginal discharge
- Diestrus: begins ~9 days after onset of standing heat & ends 60 days later (whelping if pregnancy) & has progesterone peak
- Anestrus: 80-240 days; progesterone <1 ng/mL
- To maximise conception rate and litter size, recommended to breed bitch on days 1, 3, and 5 of standing heat
- D/t long lifespan of canine sperm, fertilization occurs in the oviduct up to 8 days after coitus
28
Gestation length in dogs
65 +/- 1 days
29
Puberty in female dogs
Occurs between 6-14 months of age
| -Time of onset possibly correlates with body size
30
Onset of puberty in male dogs
- 5-12 months of age
- Initiated by secretion of LH from anterior pituitary - stimulates production of testosterone by interstitial or Leydig's cells - testicular growth is rapid & seminiferous tubules begin to differentiate & Sertoli cells form blood-testis barrier
- Secretion of FSH by anterior pituitary stimulates production of hormones by Sertoli cells, including inhibin, androgen binding protein, & estrogen
31
Follicle stimulating hormone (FSH) in male dogs
-Stimulates spermatogenesis in the presence of testosterone
32
Inhibin & estrogen in male dogs
-Provide negative feedback to the pituitary gland to decrease FSH production
33
Spermatogenesis in dogs
-Completed in 45 days, with subsequent maturation of sperm in the epididymis for ~15 days = entire process is 60 days
34
Factors impacting male dog fertility
Libido, ability to copulate, testicular size, quality of semen
- Suppression of sexual behavior & libido may occur in dogs d/t early weaning, isolation, inherited abnormalities
- Poor hind limb conformation or back trauma may affect ability to mount female
- Positive correlation between scrotal circumference and number of sperm produced
- Quality of sperm assessed by motility, morphology, volume, concentration - ejaculate (5 mL) containings ~500 million progressively motile sperm = indicator of normal fertility
35
Detection of estrus
- Cornification of vaginal epithelial cells occurs ~2 days prior to estrogen peak & 4 days prior to standing heat
- Cytology smear changes from predominantly cornified to noncornified 6 days after ovulation = the day of this change is the first day of diestrus
- Cell types on vaginal cytology: cornified epithelial cells, superficial cells (large angular w/ small nuclei), intermediate cells (round or oval w/ abundant cytoplasm & large vesicular nuclei), parabasal (small round or elongated with large well-stained nuclei, high nuclear/cytoplasmic ratio)
36
Vaginal cytology for estrus detection
Proestrus, early: intermediate and superficial cells, red blood cells, and neutrophils
Proestrus, late: superficial cells, anuclear squames,
and red blood cells
Estrus: more than 50% anuclear squames, superficial cells, ± red blood cells
Diestrus: more than 50% intermediate cells,
superficial cells, and squames early, but becoming completely noncornified with neutrophils present as diestrus proceeds
Anestrus: small numbers of parabasal cells and
intermediate cells, ± neutrophils
37
Oocyst maturation in dogs
- The ovulated oocyte is a primary oocyte that must undergo two meiotic divisions before fertilization can occur - overall maturation takes ~2 days
- After maturation, the oocyte remains viable for 4-5 days
- Optimal conception rates when bitch is bred from 4 days before to 3 days after ovulation
- Best litter size achieved when bitch is bred 2 days after ovulation
38
Placentation in dogs
Endotheliochorial placentation; Zonary; Deciduate
- Endothelium of uterine vessels lies adjacent to fetal chorion, mesenchymal, and endothelial tissues
- Maternal & fetal blood separated by 4 layers
- Zonary = placental villi arranged in a belt
- Deciduate = maternal decicidual cells are shed with fetal placentas at parturition
39
Gestation length in dogs
59-63 days
40
Implantation in dogs
- Evident by local endometrial edema 17-18 days after breeding
- No correlation between number of corpora lutea & number of fetuses in corresponding uterine horn - suggests transuterine migration of embryos
41
Pregnancy in dogs
- Luteal progesterone maintains pregnancy
- Corpora lutea retain their structural development throughout gestation
- Progesterone essential for endometrial gland growth, secretion of uterine milk, attachment of placentas, inhibition of uterine motility
- Late proestrus progesterone = 1 ng/mL
- Progesterone peaks at 30-60 ng/mL during gestation
- Progesterone falls to 4-5 ng/mL just prior to parturition
42
Pregnancy detection in dogs
- Abdominal palpation: 28-30 days after breeding = embryos and chorioallantoic vesicles form series of ovoid swellins ~2 inches in length; by day 35 uterus enlarges and difficult to palpate vesicles
- Radiology: 45 days after LH surge can confirm pregnancy & fetal age
- Ultrasound: beginning 18-22 days- gestational sacs will be ~1 cm diameter; 23-25: fetal heartbeats; 35: fetal movement
43
Gestational age on ultrasound
- Measure inner diameter of the chorionic cavity in early pregnancy
- Measure biparietal diameter in late pregnancy
- Most accurate at day 30 of pregnancy
44
Stages of parturition in dogs
-Abrupt temp drop to less than 100 F = parturition in 18-24 hr
-3 Stages
Stage 1 = 6-12 hr; uterine contractions and cervical dilation; bitch is restless, nervous, anorexic w/ panting, increased pulse
Stage 2 = 3-6 hr; fetal expulstion; release of oxytocin, Ferguson reflex; vet assistance needed if in Stage 2 for more than 5 hr without producing 1st pup, or more than 2 hr between ups
Stage 3 = placental expulsion - either immediately or within 15 min of each pup; bitch licks newborns to promote respiration, severe umbilical cords, may ingest placentas
45
Oxytocin in dog parturition
- Administered for uterine inertia, stillbirths, agalactia
| - In some cases, may also administer calcium gluconate
46
Uterine involution in dogs
- Occurs during anestrus within 4-5 weeks of parturition
- Greenish to red-brown vaginal discharge normal during this time
- Desquamation of the endometrium begins by the 6th postpartum week, with complete repair by 3 months
47
Newborn development in dogs
- 12 days: eye open
- 12-20 days: ears open
- 4.5-6 wks: start eating solid food
- 6-8 wks: weaned
48
Artifical insemination in dogs
- Using an AI catheter for intrauterine insemination results in significantly higher whelping rates than intravaginal insemination
- AI with freshly collected sperm can be done on days 1, 3, and 5 of standing heat or on days of maximum vaginal cornification
- Fresh sperm may live up to 5-6 days in reproductive tract, frozen-thawed sperm live only a few hours - therefore, ova must be mature and frozen-thawed sperm introduced 2-3 days after ovulation
49
False pregnancy (pseudocyesis) in dogs
- Common in the bitch
- Mammary gland development and lactation assoc w/ nesting or mothering behavior
- No age or breed disposition
- Occurs after the decline of serum progesterone toward end of diestrus
50
Reproductive lifespan in dogs
- Performance optimal in the bitch prior to 4 years of age
- Cycling does not cease, but after 5-8 years of age, bitches have significant decreases in conception rate & number of live pups whelped
- By 8-9 years of age, uterine pathology - cysts, hyperplasia, atrophy, neoplasia - extremely common
51
Social maturation in dogs`
18-36 months of age
- From 3-8 weeks of age, puppies most capable of learning how to interact with other dogs
- From 5-12 weeks of age, puppies most capable of learning how to interact with people
- By 10-12 weeks of age, dogs voluntarily wander and explore new environments
52
Canine infectious respiratory complex - etiology
Bordetella bronciseptica, Streptococcus equi subsp. zooepidemicus, canine parainfluenza virus (CPIV), canine influenza virus (CIV), canine respiratory coronavirus, canine adenovirus type 2 (CAV-2), canine herpesvirus, canine reovirus types 1, 2, and 3, mycoplasma, ureaplasma
53
Canine infectious respiratory complex - signs, transmission
- Mild form: loud, dry cough; sometimes productive cough with mucus; mild tracheobronchitis for 7-14 days
- Severe form: secondary bronchopneumonia; febrile, anorexic, depressed; productive cough & mucopurulent naso-ocular discharge
- Transmission: B. bronchiseptica = aerosol and direct contact; incubation period of 3-10 days
54
Canine infectious respiratory complex - pathogenesis
- Most common isolates: CPIV & B. bronchiseptica
- B. bronchiseptica attaches to cilia of upper airway epithelium, causing suppurative tracheobronchitis & bronchiolitis
- CPIV & CAV-2 usually subclinical but can cause necrotizing tracheobronchiolitis
55
Canine infectious respiratory complex - diagnosis, prevention, control
- Dx: clinical signs & known history; nasal swabs for B. bronchiseptica & mycoplasma
- Ddx: CIV, canine distemper, pneumonia, heartworm, tracheal collapse, mycotic infections, diseases causing tracheal compression
- Prevention: vaccination - should booster every 6 months when multiple animals are housed in a confined area
- Control: proper sanitation, ventilation, humidity; disinfect w/ bleach, chorhexidine, quaternary ammonium chloride
56
Canine infectious respiratory complex - treatment, research complications
- Tx: B. bronchiseptica sensitive to potentiated sulfas, chloramphenicol, quinolones, tetracyclines, gentamicin, kanamycin
- Nebulized gentamicin or kanamycin for severe cases
- Antitussives NOT when productive cough, but when coughing causing discomfort or interfering with sleep
- Bronchodilators: aminopylline, theophylline, tebutaline
- Research complications: infected animals should not be used for pulmonary studies
57
Group C Streptococcus in dogs - etiology, clin signs
- Etiology: B-hemolytic Lancefield's group C streptococcus (S. equi spp. zooepidemicus) - G(+), non-spore-forming coccus
- Clin signs: pneumonia, sepsis, coughing, weakness, fever, dyspnea, hematemesis; rapid progression similar to humans with toxic shock syndrome can occur; peracute death
58
Group C Streptococcus in dogs - transmission, pathology, pathogenesis
- S. equi spp. zooepidemicus is NOT normal commensal of dogs; most normal B-hemolytic strep in dogs are Group G
- Opportunistic pathogen & stress predisposes to disease
- Pathology: peracute - hemorrhage from mouth, nose, & in pleural cavity; ecchymotic & petechial hemorrhages; 'bull's-eye' lesions on pleural surfaces; fibrinosuppurative, necrotizing, hemorrhagic pneumonia; intracellular G(+) cocci in lung, tonsils, spleen
- Pathogenesis: stress & viral coinfection predispose; superantigens contribute to acute hemorrhagic pneumonia - bypass the conventional mechanisms of antigen presentation = hyperactive proinflammatory response & cytokine storm with IL-1B, IL-6, TNF-alpha
59
Superantigens associated with Group C streptococcus in dogs
szeF, szeN, szeP
60
Group C streptococcus in dogs - diagnosis, prevention/control, treatment
- Dx: culture of nasal swabs or tracheal lavage; PCR on postmortem lung tissue
- Ddx: bacterial pneumonias of other pathogenic Strep, Staph, E. coli, P. multocida, Pseudomonas spp, Klebsiella pneumoniae, B. bronchiseptica; respiratory disease d/t rodenticide intoxication, coagulopathies, heartworm, pulmonary thromboembolism, ruptured aneurysm, left-sided congestive heart failure
- No vaccine; quarantine infected dogs & disinfect
- Tx: antibiotic therapy based on C&S
- Dogs with severe disease not appropriate for research study
- Associated with transportation so adequate acclimation periods needed
61
Leptospirosis serovars in dogs
- Canicola, Bratislava, Grippotyphosa = renal or hepatic disease
- Icterohaemorrhagiae, Pomona = hepatic
62
Leptospirosis in dogs - clin signs, transmission
- Clin signs: subclinical; acute: lethargy, depression, abdominal discomfort, stiffness, anorexia, vomiting, muscle tenderness, pyrexia; renal failure with PU/PD, oliguria, anuria; hepatic failure with icterus, bleeding abnormalities; chronic; peracute: shock, vascular collapse, rapid death; uveitis, abortions, stillbirths, pulmonary hemorrhage
- Trnamission: wild animal reservoirs (rats, raccoons, skunks, opossums); environmental or direct contact; leptospires pass from urine into water; ZOONOTIC
63
Leptospirosis in dogs - pathology, pathogenesis
- Renal: swollen, subcapsular & cortical ecchymotic hemorrhage; chronic - small & fibrotic; endothelial cell degeneration & focal to diffuse lymphocytic-plasmacytic interstitial nephritis
- Petechia or ecchymoses & swelling of lungs
- Hepatic: diffuse hemorrhage and necrotic foci
- Pathogenesis: severity & course of disease depend on serovar & dog age and immune status; leptospires penetrate mucous membrane or abraded sin - invade vascular space and multiply rapidly - travel to renal tubular epithelium; DIC may occur secondarily
64
Leptospirosis in dogs - diagnosis, prevention, treatment
-Dx: paired serology for the microscopic agglutination test is most reliable w/ succcessive serum sampling 7-14 days after first sample; PCR
-Ddx: other causes of acute renal failure and hepatitis
-Prevention: vaccination = Quadrivalent bacterins
protect against Canicola, Icterohaemorrhagiae,
Grippotyphosa, and Pomona serovars; bivalent
bacterins cover only Canicola and Icterohaemorrhagiae; vaccination does NOT prevent carrier state
-Tx: doxycycline (if adverse effects of doxycycline, can use ampicillin or other penicillins)
-Due to zoonotic potential, infected dogs should not be used in research studies
65
Campylobacteriosis in dogs - etiology, clin signs
- Thin, curved or spiral, microaerophilic, thermophilic, motile G(-) rods
- Most common pathogenic species: C. jejuni spp. jejuni & C. coli
- Clin signs: most common in dogs <6 mths old; mucoid to watery diarrhea with/without frank blood for 5-21 days; tenesmus, inappetence, vomiting, mild fever
66
Campylobacteriosis in dogs - transmission, pathology
- Role as primary pathogen questionable; may require a coenteropathy to produce disease
- Stress or immunosuppression increase susceptibility
- Transmission: fecal-oral, mostly through contaminated food or water
- C. jejuni can be ZOONOTIC
- Pathology: enterotoxin production with dilated, fluid-filled bowel loops; cytotoxin mediated disease with friable, hemorrhagic mucosal surface; mucosa ulcerate with lymphplasmacytic infiltrate, edema and congestion or lamina propria, epithelial hyperplasia, decreased goblet cell numbers
- Visualized between enterocytes with Warthin-Starry silver-stain
67
Campylobacteriosis in dogs - pathogenesis, diagnosis
- Variety of virulence factors: enterotoxins, cytotoxins, adherence or invasion properties
- C. jejuni can cause an erosive enterocolitis by invasion of epithelium & production of cytolethal distending toxin (cdt)
- Mesenteric lymphadenitis d/t translocation to regional LNs
- Dx: highly motile, curved or spiral organisms on dark-field or phase-contrast microscopy of fresh feces; culture on selective isolation media w/ reduced oxygen tension & 37 C temp; multiplex PCR
- Ddx: any disorder than causes diarrhea in dogs
68
Campylobacteriosis in dogs - prevention, treatment
- Prevention: proper environmental sanitation, waste disposal, food storage; isolate affected individuals
- Tx: antibiotics for severely ill - erythromycin, neomycin, enrofloxacin, clindamycin, doxycycline; tx for minimum of 10-14 days
- Dogs with clinical signs should not be used for studies of digestive & absorptive functions
69
Helicobacteriosis in dogs - etiology
- G(-) microaerophilic, spiral bacteria
- Gastric helicobacters in dogs (non-Helicobacter pylori helicobacters): H. felis, H. bizzozeronii, H. salomonis, H. cynogastricus, and H. heilmannii sensu stricto
- Enterohepatic helicobacters in dogs: H. bilis, H. canis, and H. cinaedi
70
Helicobacteriosis in dogs - clin signs, transmission, pathology
- Usually subclinical; gastric infx ma have anorexia, pica, polyphagia; enterohepatic infx linked with IBD, inflammatory lesions of small intestine
- Transmission: oral-oral (less reliable in dogs) & fecal-oral
- Pathology: mild gastritis w/ reduced mucus content; vacuolation, swellin, karyolysis, karyorrhexis of parietal cells; infiltrates of plasma cells & neutrophils around blood vessels and gastric pits; intestinal lesions with lymphoplasmacytic infiltration, crypt dilation, crypt hyperplasia
71
Helicobacteriosis in dogs - pathogenesis, diagnosis
- Gastric helicobacters = urease (+) (helps survival in stomach acid)
- Enterohepatic helicobacters = urease (-), reside in large intestine, can colonize liver through portal circulation after uptake by enterocytes or through retrograde movement from intestine into bile duct
- Dx: Warthin-Starry silver stain; culture can be difficult; positive urease test on gastric biopsy sample; urea breath test; Western blot for serum antibodies; PCR of feces
- Ddx: any causes of acuteor chronic vomiting and diarrhea in dogs
72
Helicobacteriosis in dogs - prevention, treatment
- No specific prevention recommendations at this time
- Tx: Gastric spp: combination of amoxicillin, metronidazole, sucralfate (or famotidine, omeprazole, bismuth subsalicylate); recurrence rate following tx can be high; Enteroheptic spp: aminoglycosides; combo of amoxicillin, clarithromycin, metronidazole, omeprazole
- Long-term antibiotic treatment (minimum of 21 days) suggested
- Dogs used in gastrointestinal physiology or oral pharmacology studies should be free from helicobacteriosis
73
Canine parvovirus enteritis - etiology
- Etiology: Canine parvovirus strain 2 (CPV-2) - family Parvoviridae, genus Protoparvovirus, species Carnivore protoparvovirus 1
- 3 antigenic variants: 2a, 2b, 2c
- Non-enveloped, ssDNA viruses
74
Canine parvovirus enteritis - clin signs
- Clin signs: GI tract, bone marrow, myocardium, nervous tissues
- Most common is acute enteritis
- Clin signs 5 days after fecal-oral inoculation with anorexia, fever, depression, vomiting, profuse intractable diarrhea, dehydration, leukopenia; terminal illness: hypothermia, icterus, DIC d/t endotoxemia
75
Canine parvovirus enteritis - transmission, pathogenesis
- 6-20 weeks of age most susceptible; can infect any age
- Puppies less than 6 weeks protected by passive maternal antibody
- CPV-2c assoc w/ severe disease in vaccinated adults
- Has affinity for rapidly dividing cells of intestine - acute enteritis with intestinal crypt necrosis, villus atrophy
- Also tropism for bone marrow and lymphoid tissues - leukopenia and lymphoid depletion
76
Canine parvovirus enteritis - diagnosis, prevention/control, treatment
- Dx: ELISA (can be falsely negative d/t brief, intermittent shedding; PCR; necropsy - necrosis & diltation of intestinal crypt cells with secondary villous collapse
- Quarantine positive animals for at least 10 days (shedding in feces)
- Disinfect areas with 1:30 bleach or commercial disinfectant; vaccinate 6 week old puppies every 2-4 weeks with MLV vaccine until at least 16 wks old
- Tx: supportive care
- Do not use dogs with parvovirus enteritis on research study
77
Rabies in dogs - clin signs, pathogenesis
- Lyssavirus in family Rhabdoviridae
- Clin signs: 3 stages
- Stage 1 = prodromal stage with loss of instinctive fear of humans by wild animals
- Stage 2 = furious stage where animals easily excited or hyperreactive
- Stage 3 = paralytic with incoordination and ascending ataxia of hindlibs d/t viral-induced damage of motor neurons; death occurs d/t respiratory failure
- Transmission: from wild animal saliva, typically bite wounds
- Pathogenesis: 3-8 week incubation period (can range from 1 week to 1 year); bites to head and neck have shorter incubation period
- Virus migrates centripetally via peripheral nerve fibers to neurons within brain - virus migrate centrifugally to salivary glands - shedding & transmission via saliva
78
Rabies in dogs - diagnosis, prevention
- Dx: definitive dx is immunofluorescence of virus in Negri bodies of hippocampal cells
- Ddx: pseudorabies, canine distemper, bacterial meningitis, toxicants
- Vaccinate puppies by 16 weeks, again at 1 year, then annually or triennially depending on state and local laws
- Immunoprophylaxis recommended for personnel with work-related risks of exposure
79
Giardiasis in dogs
- Giardia lamblia (aka G. duodenalis, G. intestinalis) - binucleate flagellate protozoan
- Clin signs: usually in young dogs; voluminous light-colored, foul-smelling diarrhea
- Transmission: direct life cycle with infected from cyst-contaminated food or water
- Change in pH from stomach to duodenum activates excystation and trophozoites than attach to enterocytes
- Dx: direct fecal smear for trophozoites; zinc sulfate centrifugation for cysts; ELISA available but PPV is poor; PCR
- Ddx: bacterial and protozoal enteritis, coccidiosis, whipworms
- Tx: metronidazole for 5-10 days; albendazole, fenbendazole, pyrantel, praziquantel
80
Coccidiosis in dogs
- Isospora canis, Isospora ohioensis, I. neorivolta, I. burrowsi, Hammondia heydorni
- Oocysts can be found in clinically healthy animals & ones with diarrhea
- Clin signs: diarrhea +/- blood or mucus; vomiting, dehydration, lethargy, weight loss
- Transmission: fecal-oral oocysts, monozoic cysts in intermediate host tssues
- Life cycle both sexual & asexual; unsporulated eggs released & sporulate under appropriate environmental conditions
- Ddx: other causes of diarrhea
- Tx: may not be necessary as typically self-limiting; sulfadimethoxine, trimethoprim sulfa
81
Ascarids of dogs
- Toxocara canis (most common), Toxacaris leonina
- Clin signs: usually in young dogs with large worm burdens; diarrhea, vomiting, dehydration, abdominal discomfort with vocalization; "potbellied"; intussusception or intestinal obstruction; puppies can have lung migrations & fatal pneumonia
- Tranmission: transplacental & transmammary migration; ingestion of infective eggs
- Dx: fecal flotation
- Prevention: monthly milbemycin or ivermectin plus pyrantel pamoate
- Puppies should be treated early & often (every other week until 16 wks)
- Pregnant bitches can be treated with extended fenbendazole from day 40 of gestation through day 14 of lactation
82
What is the infective stage of Toxocara canis?
Third-stage larva (L3)
83
Hookworms in dogs
- Anclystoma caninum (most common), A. braziliense
- Only A. caninum typically results in illness
- Clin signs: puppies - anemia, bloody diarrhea, melena; lethargy, anorexia, dehydration, vomiting, poor weight gain
- Transmission: L3 larvae ingested from environment & develop in intestinal tract; transmammary from ingestion of paratenic host, less commonly transplacental
- Dx: eggs or larvae on fecal flotation or direct smear
- Ddx: paravovirus for bloody diarrhea; autoimmune hemolytic anemia for young dogs with anemia
- Treatment: pyrantel pamoate (safest for young ill animals); monthly milbemycin or ivermectin + pyrantel pamoate
- D/t transplacental or milkborne infection, puppies should be treated every 2 weeks from 2 to 16 weeks old
84
What is the infected stage of Anclystoma caninum?
Third-stage larva (L3)
85
Whipworms in dogs
- Trichuris vulpis
- Adult worm resides in cecum or ascending colon
- Clin signs: mostly subclinical; diarrhea with blood/mucus, abdominal pain, anorexia, weight loss; eosinophilia, anemia, hypoproteinemia
- Direct life cycle with eggs passed in feces; adult worm penetrates enteric mucosa - inflammation causes ciarrhea
- Dx: fecal flotation - barrel shaped thick walled eggs with bipolar plugs; adult worm release eggs intermittently = negative fecal does not exclude infx
- Ddx: giardiasis, coccidiosis, bacterial enteritis
- Tx: fenbendazole, oxibendazole, milbemycin; treat monthly for 3 months
86
Cestodes in dogs
- Dipylidium caninum (most common); Taenia pisiformis, Echinococcus granulosus, Multiceps spp, Mesocestoides spp, Spirometra spp.
- Clin signs: mostly subclinical; severe infestation can cause diarrhea, weight loss, poor growth
- Indirect life cycle = require fleas or lice as intermediate host; ingestion of arthropods transmits tapeworm
- Dx: egg capsules or proglottids on surface of feces or around the anus
- Tx: praziquantel orally or SC is the standard tx; fenbendazole, mebendazole, oxfendazole
87
Demodicosis in dogs
- Demodex canis - commensal mite that lives in hair follicles & is passed from dams to nursing pups
- Clin signs: alopecia, erythema, pruritis, crusts, hyperpigmentation esp on feet, face, around ears
- Localized vs. generalized - indicates underling immunosuppression
- Dx: cigar shape mite on deep skin scrape
- Ddx: dermatophytosis, allergic contact dermatitis, seborrheic dermatitis, bacterial pyoderma
- Tx: ivermectin; oral milbemycin
88
Sarcoptic mange in dogs
- Sarcoptes scabiei var. canis
- ZOONOTIC
- Clin signs: intense pruritis, usually beginning at sparsely furred areas of ear pinnae, elbows, ventral thorax, abdomen; alopecia, yellowish dry crusts with macular papular eruption
- Dx: superficial skin scrapins show adult mites, mite eggs, mire feces; anti-mite IgE in serum or via intradermal antigen test; histo: small foci of edema, exocytosis, degeneration, necrosis
- Ddx: flea allergy dermatitis
- Tx: even if scrapings negative, if clin signs consistent a treatment trial should be done; also treat kennel mates as contagious; ivermcin or milbemycin
89
Ticks of dogs
- Genera that commonly infest dogs in US: Rhipicephalus, Dermacentor, Amblyomma, Ixodes
- Vector-borne tick diseases: Rocky Mountain spotter fever (Rickettsia rickettsii), Lyme disease (Borrelia burgdorferi sensu stricto), thrombocytic anaplasmosis (Anaplasma platys), canine monocytic ehrlichiosis (Ehrlichia canis)
- Clin signs: ticks alone cause minimal signs unless dog has hypersensitivity rxn
- Dermacentor anersoni & Dermacentor variabilis produce salivary neurotoxin that causes ascending flaccid paralysis; dogs usually show improvement within 24 hr of tick removal & complete recovery within 72 hr
- Tx: formamidines (amitraz), pyrethroids, phenylpyrazoles (fiproni)
- Ddx: for tick bite paralysis - botulism, snakebite, polyradiculoneuritis, idiopathic polyneuropathy
90
Fleas in dogs
- Ctenocephalides felis felis (most common to infest dogs)
- Clin signs: foci of alopecia, pruritis; dogs that are hypersensitive to antigenic proteins in flea saliva develop flea allergy dermatitis w/ crusting, excoriations over lumbosacral region, flanks, thighs, abdomen
- Fleas can transmit Dipylidium tapeworms
- Dx: presence of fleas or flea excrement in coat
- Tx: integrated pest management approach to target adult & immature fleas and environment
- Ovicidal tx = lufenuron & selamectin
- Adulticidal tx = fipronil, spinosad, selamectin, imidacloprid
- Ddx: mites, bacterial folliculitis, allergic or atopic conditions
91
Superficial dermatophytoses in dogs
- Microsporum spp, Trichophyton spp, Epidermophyton spp
- Clin signs: circular areas of alopecia & crusting with or without follicular papules, usu around face, neck, forelimbs
- Dermatophytes infect the hair shaft and follicle, as well as surrounding skin - hairs become brittle and broken shafts remain infective in environment for mths
- ZOONOTIC
- Dx: dermatophyte test medium for culture; use toothbrush method to come hairs and scales from several infected sites then press into culture media; positive cultures will become red at the same time as growth of a fluffy white colony
- Tx: systemic: grseofulvin, ketoconazole, itraconazole, fluconazole; topical: antifungal shampoos, rinses, creams; isolate infected animals
- Disinfect with lime sulfur, enilconazole, or bleach for environmental spores (chlorhexidine & Virkon ineffective)
92
Hypothyroidism in dogs - etiology
- Etiology: primary is dysfunction of thyroid gland; secondary is dysfunction of pituitary glands; majority of cases are d/t lymphocytic thyroiditis (an autoimmune disorder) or idiopathic atrophy of the thyroid gland; rarely, congenital defects or nonfunctional tumors may cause hypothyroidism
- Lymphocytic thyroiditis is the major cause in lab beagles & appears to be familial
93
Hypothyroidism in dogs - clin signs
-Clin signs: hypothyroidism reduces metabolic rate: obesity, lethargy, cold intolerance, constipation; dermatologic abnormalities: nonpruritic bilaterally symmetric alopecia, hyperpigmentation, seborrhea, pyoderma; increased serum cholesterol & triglycerides d/t a decrease in lipolysis and decreased numbers of low-density lipopolysaccharide receptors; normocytic normochromic nonregenerative anemia; increased ALP & CK; neuro signs: hypothyroidism, lameness, foot dragging, paresis d/t several mechanisms such as segmental nerve demyelination or nerve entrapment secondary to myxedema, Horner's syndrome, facial nerve paralysis, megaesophagus, laryngeal paralysis; myopathies d/t metabolic dysfunction and atrophy of type II muscle fibers; cardiovascular abnormalities: bradycardia, hypocontractility, increased vascular volume, atherosclerosis, decrease in P- and R-wave amplitude, inverted T waves - ECG abnormalities are d/t lowered activity of ATPases and Ca channel function
94
Association between hypothyroidism and von Willebrand disease in dogs
- Has been suggested but not confirmed
- Hypothyroidism does not appear to cause overt, clinical von Willebrand disease, but may exacerbate existing subclinical von Willebrand disease
95
Hypothyroidism in dogs - epizootiology
- Middle-aged, larger breed dogs; higher incidence in spayed females
- Doberman pinschers, golden retrievers, laboratory beagles
96
Hypothyroidism in dogs - diagnosis
- Dx: measurement or serum total T4 (thyroxine) and free T4; T4 serves primarily as a precursor for T3 and is heavily protein bound
- Total T4 is good screening tool with sensitivity of around 95%
- T3 is most biologically active form, but is unreliable measurement of serum T3 levels; in addition, T3 may be preferentially released and conversion of T4 to T3 may be enhanced by the failing thyroid, particularly early in disease
- Autoantibodies can be responsible for false elecations in the concentrations of T3 and T4
- Free T4, measured by equilibrium dialysis, should be assayed in dogs that are suspected of hypothyroidism and have autoantibodies with normal or high T3 and T4
- Endogenous TSH levels can be normal in some dogs with hypothyroidism & high TSH have been noted in normal dogs and sick animals that are actually euthyroid; TSH stimulation using exogenous bovine TSH is a reliable method for diagnosis - must postpone testing for 4 weeks if thyroid supplementation has been given
- Normal response to administration of TSH is increase of T4 levels at least 2 ug/dL above the baseline levels or an absolute level that exceeds 3 ug/dL
97
What drugs can falsely lower T4 values in dogs?
Glucocorticoids, anticonvulsants, phenylbutazone, salicylates
98
Hypothyroidism in dogs - treatment
- L-thyroxine (sodium levothyroxine) 0.01-0.02 mg/kg once a day
- After beginning supplementation, recheck thyroid level in 6-8 weeks; should also see clinical response in 6-8 wks with weight loss, hair regrowth
- Neuro signs do not always go away
99
Obesity in dogs
- Body weight 20-25% over the ideal
- Breeds predisposed: Labrador retrievers, Cairn terriers, dachshunds, basset hounds, golden retrievers, cocker spaniels, beagles
- Spay, neuter, hypothyroidism, hyperadrenocorticism can contribute to obesity
- Ultraouns can be used to measure SC fat in dogs; measurements of lumbar area can reliably predict total body fat
- Tx: restrict intake to 60% of calculated energy requirement to maintain ideal weight; restriction down to 50% produces no adverse health effects
- T3 levels will decrease in direct proportion with caloric intake
- Ideally weight loss is 1-2% of body weight per week
- Fiber does NOT impact satiety in dogs and therefore does not have a beneficial effect in weight loss protocols
- Research complications: impacts metabolism, joint health, risk for diabetes mellitus & metabolic disease (hyperinsulinemia, hypoadiponectinemia; seen in ~20% of obese dogs), risk of cardiac disease, hypertension, respiratory tract compromise
100
Traumatic wounds in dogs
- Abrasion: sustained by shear forces; partial thickness skin wounds characterized by minimal bleeding or tissue disruption
- Puncture: small surface opening but penetrate into deep tissues with the potential for contamination
- Laceration: sharp separation of skin that may extend to deeper tissues
- Classification of traumatic wounds: clean, clean-contaminated, contaminated, dirty
- Control bleeding with direct pressure; tourniquets are discouraged
- 8 psi is required to obtain adequate tissue irrigation - can obtain using a 35-ml syringe with an 18- or 19-gauge needle
- Primary wound closure is the treatment of choice for clean and clean-contaminated wounds
- Delayed primary closure - closure within 3-5 days of wounding (prior to the formation of granulation tissue)
- Secondary closure - when the wound is closed after 5 days
- SC closure should be performed with absorbable suture such as polydioxanone, polyglactin 910, or polyglycolic acid
- Antibiotic choices: cephalosporings, amoxicillin-clavulanate, trimethoprim sulfas
101
Pressure sores (decubital ulcers) in dogs
- Often develop over bony prominences - elbow, tuber ischii, tarsus, carpus
- Compression of soft tissues between hard surfaces: vascular occlusion, ischemia, tissue death
- Risk factors: poor hygiene, self-trauma, low-protein diet, preexisting tissue damage, muscle wasting, inadequate bedding, ill-fitting coaptation devices
- Skin initially appears red, irritated; over time full thickness skin defects & necrosis
- Large breed dogs may be predisposed
- Prevention: provide adequate padding for long periods of recumbency; move recumbent animals every 2 hr; clip, bathe, and dry any areas of urine scalding; maintain appropriate body weight via appropriate diet
- Tx: deep wounds - radiograph for bony involvement; debridement, closure; bandage all full thickness wounds with a doughnut technique; remove bandages 1-2x daily
102
Acral lick granuloma in dogs
- Skin lesion caused by self-trauma d/t initial irritation d/t a neurologic or orthopedic condition, allergy
- Self-trauma may release endogenous endorphins = reward for the abnormal behavior
- Seen most often in large breed dogs, particularly Dobermans
- Clin signs: irritated, hairless areas on distal extremities; ulceration, hyperpigmentation
- Ddx: bacterial or fungal infection, foreign body, pressure sore, mast cell tumor or other neoplasia
- Prevention: behavior modification & relief of boredom
- Tx: E-collar; topical treatment (steroids, intralesional cobra venom), acupuncture, radiation, surgery; naltrexone & nalmefene reduce excessive licking behaviors - opioid antagnoists; psychoactive drugs for boredom or anxiety - phenobarbital, megestrol acetate, progestins; clomipramine for compulsive anxiety disorder
103
Elbow hygromas in dogs
- Fluid-filled sacs that develop d/t repeated trauma or pressure over a the olecranon (can also see hygromas at tuber calcis, greater trochanter, stifle)
- Most common in large & giant breeds; less than 2 yr of age
- Clin signs: initially painless, fluctuant swelling over elbow - progress to inflamed & ulcerated
- Pathology: cavity is lined by granulation & fibrous tissue; fluid is yellow or red serous transudate, less viscous than joint fluid & hygromas do NOT communicate with joint
- Tx: conservative = relieve pressure at joint w/ padding hard surfaces, doughnut bandage; surgery for complicated cases
- Drainage & steroids NOT recommended d/t risk of infx
- Recurrence likely unless predisposing factors addressed
104
Are hygromas true cysts?
No - because lack an epithelial lining
105
Corneal ulcers in dogs
- Due to direct trauma, contact with chemicals, exposure to drying during anesthesia
- Clin signs: blepharospasm, epiphora, photophobia; swelling of periocular tissues
- Dx: fluorescein stain; inspect for underlying foreign body, abnormal eyelids, aberrant cilia
- Tx: topical antibiotic ointment
- Simple corneal ulcers should show healing after 3 days - if not healed at 3 days, may have undermined edge impeding healing: apply topical anesthetic & use cotton applicator to roll over surface of ulcer toward its edge
- Deep ulcer may need debridement & primary repair
106
Implant & catheter infections in dogs
- Common source of infection = colonization of the device from an external component
- Secondary lesions include traumati cardiac lesions, visceral infarcts, fatal hemorrhages
- 'T' connector assoc w/ more infection than 'Y' connector
- Tx: almost always requires removal or catheter or implant; superficial wound irritation/infx may be treated locally with antibiotics & sterile dressings
- If catheter retention is important, catheter lumen may be disinfected with chlorine dioxide solution - after 15 min, solution is removed & replaced with heparinized saline
- IV catheters for drug delivery: place in vena cava & NOT right atrium, thereby minimizing trauma to tricuspid valve
- Long extension tubing connected to the port may reduce potential for infection
- Prevention: disinfect catheter, coat with antibiotic ointment & rebandage every other day; one a month, catheter line may be disinfected with chlorine dioxide; can also use solution of ceftazidimine alternated with heparin locking solution
107
Sepsis in dogs
- Sepsis = the systemic response to infection caused by bacteria, fungi, or viruses
- Early sepsis (hyperdynamic sepsis): increased HR, red MMs, normal to increased CRT, febrile
- Late sepsis: septic shock with decreased temp, palp MMs, prolonged CRT, decreased cardiac output & BP, peripheral edema, confusion
- Pathogenesis: mediated by immune responses involving mediators such as cytokines, eicosinoids, complement, superoxide radicals, nitric oxide - inflammation is left unchecked & system unable to compensate - cardiovascular collapse
- Dx: clin signs, increased or decreased WBC, increased immature neutrophils, decreased platelet count, decreased BP, hypoxemia, altered cardiac output
- Ddx: pancreatitis, trauma
- Tx: support cardiovascular system (fluids), remove septic focus (antibiotics; often G(-) bacteria of GI origin; IV broad spectrum bactericidal); block mediators of systemic response (steroids, NSAIDs, antibodies, etc.)
108
Aspiration lung injury in dogs
- Misplacement of gastric tubes, complication of anesthesia
- Aspiration provokes an inflammatory response (cytokines) = rapid influx of neutrophils into lung parenchyma & alveolar spaces - leads to alveolar collapse; increased vascular permeability & leakage of fluid in alveolar spaces; infx may complicate within 24-48 hr
- Clin sign: depend on pH, osmolality & volume of aspirate; cough, increased RR & resp effort, fever, decreased O2 sat
- Bronchoalveolar pattern on radiographs in cranioventral lung fields
- Tx: largely supportive; suction at time if aspiration observed; oxygen therapy; +/- fluids (don't want volume overload & colloids can increase vascular permeability in lungs); antibiotics (amoxi-clav first line)
- Prevention: fast 12 hr for food & 2 hr for water prior to anesthesia
109
Thermal burn wounds in dogs
- External heating devices
- Results in desiccation of tissue & coagulation of proteins; injured area surrounded by zone of vascular stasis that promotes additional tissue damage
- Uncomplicated, superficial burns heal by reepithelialization within 3-5 days
- Deeper burns have central area of nonviable tissue surrounded by edematous, inflamed tissue - a thick eschar, composed of coagulated proteins & desiccated tissue fluids - develops over deep burns; deep burns heal by granulation under the eschar
- Pain management (deep burns theoretically less painful than superficial d/t destruction of nerve endings)
- Tx: immediate exposure to cool water (15 C) to reduce edema & pain; topical wound dressings; antibiotic ointment on wound surface (systemic antibiotics cannot penetrate eschar & not well distributed at burn site d/t vascular damage); use silver sulfadiazene & povidone-iodine, mafenide (G(-) coverage); cover with nonadherent dressing (less painful than noncovered burns); may need to surgically remove eschar to improve healing
- Prevention: avoid electric heating pads & heat lamps
110
Chemical burn injury in dogs
- Skin contact with concentrated disinfectants, lab chemicals; perivascular injection of pentobarbital, thiamylal, thiopental, thiacetarsemide, vincristine, vinblastine, doxorubicin
- MOA depends on pH, osmolality and chemical composition: oxidation, reduction, disruption of lipid membranes, other rxns
- Clin signs: mild irritation & redness; many agents cause progressive injury until chemical rxn neutralized - necrosis, secondary infx develop
- Tx: thorough & repeated lavage; perivascular injection - dilute with SC saline injectons, local steroid infiltration; topical application of DMSO or dexrazoxane (free radical scavengers); local infiltration of hyaluronidase + warm compresses for perivascular vinblastine or doxorubicin; early excision may prevent excessive sloughing d/t doxorubicin; analgesia
- Prevention: access to central rather than peripheral vessel; if using peripheral catheter, follow with vigorous saline flushing; give repeated injections in NEW catheters at DIFFERENT sites
111
Radiation burn injury in dogs
- Result of free oxygen radical formation; damage to epithelial layers can lead to desquamation; injury to fibroblasts results in decreased collagen production& poor wound healing; fibrosis of blood vessels & subsequent hypoxia & necrosis of deeper tissues
- Clin signs: hair loss, erythema, clear exudate; deeper injury: SC fibrosis, deep tissue necrosis
- Tx: special feeding with oral MM damage, excise avascular tissue; silver sulfadiazene, mafenide acetate, other topicals to control infection
- Prevention: appropriate, fractionated therapy & application of shielding; wait 1 week or longer before administering radiation to a surgical site; avoid surgeries for 1-2 mths after radiation
112
Common neoplasias in laboratory beagles
Males: lymphoma, sarcoma (incl hemangiosarcoma of skin & fibrosarcoma)
Females: mammary, lymphoma, sarcoma (mast cell tumors)
-Beagles also at risk for thyroid neoplasia
113
Appropriate tumor margins in dogs
- At least 1 cm around tumor
| - If mast cell suspected: at least 3 cm around tumor
114
Lymphoma in dogs
- 5-7% of canine tumors; 85% of canine hematopoetic disease; majority are multicentric high-grade lymphoma (MHGL)
- Tobacco smoke, environmental chemicals, waste emissions possible risk factors
- Clin signs: painless enlarged LNs, anorexia, weight loss, polyuria, polydipsia, fever, lethargy, organomegaly = MHGL
- Less common: alimentary, (vomiting, diarrhea) mediastinal (respiratory signs secondary to pleural effusion, cranial vena cava syndrome; hypercalcemia w/ PU/PD, weakness), cutaneous (mycosis fungoides; typically CD8+ T cell immunophenotype; skin lesions), extranodal (eyes, CNS, kidneys, nasal cavity) lymphomas
115
Lymphoma in dogs - epizootiology, diagnosis
- Incidence highest in dogs 5-11 yr old
- No gender predilection
- Dx: FNA of LNs; thoracic radiographs & abdominal U/S; FNA of liver or spleen; CBC/chem; flow cytometry for immunotyping, bone marrow aspiration, surgical lymphadenectomy & histology
- Pathology: LN cortex vs. medulla definition lost; multiple nodular masses in spleen; enlarged liver with disseminated nodules; nodular & diffuse growths in GI tract
116
Classification of lymphomas in dogs
- Based on cytological, morphological, immunological characteristics used the Kiel classification criteria
- Most common: high grade & large-cell (histiocytic)
117
Lymphoma in dogs - pathogenesis, diff diagnosis, treatment
- All lymphomas should be considered malignant
- Average survival time of dogs without treatment is 4-6 weeks; median survival time with aggressive therapy is <12 mths
- Hypercalcemia is a paraneoplastic syndrome common w/ lymphoma - may be d/t a parathormone-like substance produced by the neoplastic lymphocytes
- Ddx: systemic mycosis; salmon-poisoning & other rickettsial infections; lymph node hyperplasia d/t viral, bacterial, immunologic causes; dermatopathic lymphadenopathy; other GI tumors, foreign bodies, lymphocytic-plasmacytic enteritis
- Tx: chemotherapy, radiation, bone marrow transplantation; most treatment is palliative
- Euthanasia should be considered for affected research animals d/t grave prognosis
118
Mast cell tumors in dogs - etiology, clin signs
- Derived from CD344+ bone marrow progenitor cells
- Most common skin tumor of dog (up to 21% of canine skin tumors)
- Mast cells normally found in connective tissue beneath serous surfaces & MMs, within skin, lung, liver, GI tract
- Risk factors: breed, genetics, chronic inflammation, mutations in the surface growth factor
- Clin signs: typically solitary, well-circumscribed, slow-growing 1- to 10 cm nodules in the dermis & SC; alopecia; irritation, inflammation, edema of surrounding tissue; frequently on trunk & hind limb extremeties, preputial & perineal areas
- If abdominal organs involved, may see anorexia, vomiting, melena, abdominal pain, GI ulceration
119
Which mast cell locations in dogs are associated with greater predilection for recurrence or metastasis?
Perineal, preputial & inguinal areas
120
Mast cell tumors in dogs - pathology, diagnosis
- Middle-aged dogs usually
- Patanik classification & grading system
- Grade I: well differentiated, best prognois
- Grade II: intermediate differentiation
- Grade III: anaplstic or undifferentiated; large irregular nuclei; mitotic figures; cells are pleomorphic w/ indistinct borders; most likely to disseminatee internally - usually spread to regional LNs, spleen, liver, kidneys, lungs, heart
- Dx: toludine blue stains cytoplasmic granules red or purple; can also stain granules with Wright's, Giemsa, & Romanowsky stains; mast cells may contain tryptase, chymase, or both
- Tx: wide surgical excision (3 cm margins); may follow w/ radiation, chemotherapy, glucocorticoid therapy; aspiration or surgical removal of regional LNs recommended if lymphatic tumor drainage suspected; if tumor not completely resectable - debulking surgery and adjunct therapy
121
Mast cell tumors & gastric ulcers
- Ulcers in the fundus, pylorus, proximal duodenum
- Likely secondary to tumor production of histamine
- Histamine stimulates the H2 receptors of the gastric parietal cells = increased acid secretion
122
Research complications of mast cell tumors in dogs
- Because of potential for systemic release of histamine, vasoactive substances, heparin, eosinophilic chemotactic factor, proteolytic enzymes & possible delayed wound healing & tumor recurrence - NOT good study candidates
- Grade I tumors may be excised allowing dogs to stay on study; Grade II is variable - monitor for recurrence monthly & evaluate buffy coat every 3-6 months for systemic mastocytosis; Grade III does not warrant treatment in research setting
123
Canine transmissible venereal tumors
- AKA infectious or venereal granuloma, Sticker tumor, transmissible sarcoma, contagious venereal tumor
- Transmitted horizontally to genitals by coitus
- Originated from dogs or wolves thousands or years ago; oldest known continuously passaged somatic cell line
- Round cell tumor of histiocytic origin
- Most prevalent in tropical & temperate climates
124
Canine transmissible venereal tumors - clinical signs, transmission, pathology
- Clin signs: usually cauliflower-like masses on external genitalia; friable; hemorrhage is common
- Males: bulbus glandis or glans penis
- Females: posterior vagina at junction of vestibule & vagina
- Most common in young sexually active dogs
- Transmission: during coitus when injury to genitalia allows or exfoliation & transplantation
- Pathology: sheets or compact masses of round, ovoid or polyhedral cells; large round nuclei with coarse chromatin; cytoplasms is eosinophilic with small vacuoles in "string of pearls" pattern
- Tumor growth occurs within 2-6 mths after mating, then growth generally slows; metastasis is rare - may involve superficial inguinal & external iliac LNs & distant sites
- Spontaneous regression may occur within 6-9 months of tumor development
125
Canine transmissible venereal tumors - diagnosis, treatment
- Dx: cytology; histopathology of biopsy
- Ddx: lymphoma, histiocytoma, mast cell tumor, amelanotic melanoma
- Prevention: thorough PE prior to breeding; remove affected animals from colony to stop further spread
- Tx: chemotherapy with vincristine for 4-6 weeks most effective; also surgery & radiation
- Experimental implantation of CTVTs elicits formation of tumor-specific IgG - may interfere with immunologic studies
126
Mammary gland tumors in dogs
- Usually single nodules in dogs; usually in the two most caudal glands (4th & 5th)
- Benign tumors are small, well circumscribed, firm
- Malignant tumors tend to be larger, invasive, coalescent with adjacent tissues
- Inflammatory mammary carcinomas may mimic mastitis, severe dermatitis
- Median age 10-11 years; uncommon in dogs <5 years
- Can occur in males assoc w/ endocrine abnormalities (like estrogen-secreting Sertoli cell tumors)
127
Mammary gland tumors in dogs - pathology
- T (tumor size), N (lymph node involvement), & M (metastasis) staging system
- About half are benign (fibroadenoma, simple adenoma, benign mesenchymal tumor), half malignant (solid carcinomas, tubular adenocarcinomas, sarcomas, carcinosarcomas)
- Histologic grades based on tubule formation, nuclear pleomorphism, mitosis
- Develop under the influence of hormones (60-70% are estrogen & progesterone positive)
- Malignant tumors typically spread through lymphatic vessels; 1st-3rd glands drain to ipsilateral axillary or anterior sternal LNs; 4th-5th drain to superficial inguinal LNs
128
Mammary gland tumors in dogs - diagnosis, treatment
- Ddx: mammary hyperplasia, mastitis, severe dermatitis
- Dx: FNA, radiographs & ultrasound for metastatic disease
- Prevention: lifetime risk reduced to 0.5% by spaying prior to first estrus; spayed after 1st estrus - 8%, 2nd estrus - 26%
- Tx: surgery (2 cm margins); multiple tumors removed via chain mastectomies
- Treatment of early-stage or low-grade tumors may allow dogs to continue on study, but should be monitored regularly for recurrence
129
Congenital defects documented in beagles
Brachyury (short tail), spina bifida, pulmonic stenosis, cleft palate–cleft lip complex, deafness,
cataracts, glaucoma, microphthalmos, optic nerve
hypoplasia, retinal dysplasia, tapetal hypoplasia, factor
VII deficiency, pyruvate kinase deficiency, pancreatic
hypoplasia, epilepsy, GM1 gangliosidosis, globoid cell
leukodystrophy, XX sex reversal, cutaneous asthenia (Ehlers–Danlos syndrome), cryptorchidism, monorchidism, limb deformity, inguinal hernia, diaphragmatic hernia, hydrocephaly, and fetal anasarca
-Each of these has <1% incidence
130
Benign prostatic hyperplasia in dogs
- Age-related condition in intact males
- Response to presence of both testosterone & estrogen
- Clin signs: subclinical; tenesmus, urethral discharge (yellow to red), hematuria
- Usually dogs >4 years; ~95% of intact males will develop by 9 years of age
- Pathology: hyperplasia of prostatic glandular tissue; eventually hyperplasia becomes cystic; prostate becomes more vascular with honeycomb appearance (hematuria, hemorrhagic discharge)
- Increased production of estrone & estradiol + decreased secretion of androgens sensitizes prostatic androgen receptors to dihydrotestosterone; presence of estrogen may also increased number of androgen receptors & hyperplastic glands also have increased ability to metabolize testosterone to 5alpha-dihydrotestosteron
- Ddx: squamous metaplasia, paraprostatic cysts, bacterial prostatitis, prostatic abscessation, prostatic neoplasia (adenocarcinoma)
- Prevention: castration
- Tx: castration results in prostate involution within 7-10 days; hormone therapy with estrogens (applicable is semen collection necessary)
- Can interfere with research studies of steroidal hormones & neither castration nor estrogen therapy is compatible with study continuation; tenesmus may impact studies of colorectal or anal function
131
Hormone therapies for benign prostatic hyperplasia in dogs
- Finasteride: synthetic 5alpha-reductase inhibitor - limits metabolism of testosterone
- Gonadotropin-releasin hormone analogs (desorelin) - inhibit production of testosterone & estrogen via negative feedback on hypothalamus-pituitary axis
132
Benign prostatic hyperplasia in dogs as a research model
-Used to evaluate the use of ultrasonic histotripsy as a precise nonsurgical urethral-sparing alternative to prostate surgery
133
Juvenile polyarteritis syndrome in dogs
- AKA steroid-responsive meningitis-arteritis
- Seen in young beagles (occasionally other breeds)
- Caused by systemic necrotizing vasculitis; may have auto-immune component and/or hereditary component
- Clin signs: fever, anorexia, lethargy, reluctance to move head and neck; pain when neck region touched; proprioceptive deficits, paresis, paralysis
- Typically has a course of remissions & relapses w/ 3-7 days of illness & 2- weeks of remission
134
Juvenile polyarteritis syndrome in dogs - trnamission, pathology
- 6-40 month old beagles; Welsh Springer Spaniels
- No sex predilection
- Pathology: foci of hemorrhage in heart coronary grooves, cranial mediastinum, cervical spinal cord meninges; local LNs enlarged & hemorrhagic; necrotizing vasculitis & pervasculitis or small to medium size arteries; arterial fibrinoid necrosis leading to thyroid gland hemorrhage & inflammation; inflammatory cells (mostly neutrophils) surround arteries
- Initiating factors unknown; immune mediation strongly suspected - affected dogs have elevated alpha2-globulin fractions & abnormal immunologic responses
- Offspring of certain sires more likely to be affected; breeding 2 affected dogs = 1 in 7 puppies affected
135
Juvenile polyarteritis syndrome in dogs - diagnosis, treatment
- Ddx: encephalitis, meningitis, injury, degeneration of cervical vertebrae or disks; arthritis
- No known prevention of control measures
- Tx: corticosteroids abate clinical signs; withdrawal of steroids leads to return of signs within weeks
- Severe clinical signs & need for immunosuppressive treatment is often incompatible with research; unknown whether subclinical necrotizing vasculitis causes sufficient aberrations to measurably alter immunologic responses
136
Interdigital cysts in dogs
- Chronic inflammatory lesions (not true cysts) in webbing between the toes
- Clin signs: lameness; licking & chewing at interdigital space; exudation; matted hair
- Common in German shepherds, research beagles
- Usually occur at 3rd or 4th interdigital space
- Predisposing factors: type of caging, body condition score, age, location of cyst, chronic interdigital dermatitis
- Histo: pyogranulomatous inflammation
- Cause for initial development of cyst unknown
- Ddx: bacterial infection, bony lesions, neoplasia
- Tx: if sterile, systemic corticosteroids; if bacteria: antibiotics also; surgery = removal of lesion & interdigital web with 2 layer closure of adjacent skin and soft tissues; place foot in padded bandage when weight-bearing
- Tend to recur
137
Hyperplasia of the gland of the nictitating membrane in dogs
- AKA 'cherry eye'
- Prolapse of gland of the nictitating membrane
- Breeding disposition, including beagles
- Specific etiology unknown
- Clin signs: glandular tissue of nictitating membrane protrudes beyond edge in ventromedial aspect of orbit; excessive tearing to mucoid discharge; corneal erosion in severe cases
- May be d/t congenital weakness of the connective tissue band between the gland and the cartilage of the nictitating membrane
- Tx: corticosteroids (topical or systemic) to reduce glandular swelling; surgical reduction or excision typically required to resolve condition
- Gland is important for tear production; although rest of lacrimal glands should be sufficient for adequate tear production, removal has possible consequence of keatoconjunctivitis sicca
