Infectious Disease Flashcards
What breeds (dog and cat) are predisposed to Mycobacterium avium?
- Bassetts
2. Siamese
Where does the life cycle of Pneumocystis carinii occur?
The entire life cycle occurs within the alveolar spaces (trophozoites and cysts)
Clinical disease with Pneumocystis carinii occurs in what scenarios?
- Immunosuppression
- Crowding
- Distemper patients
What is the pathophysiology behind Pneumocystis carinii?
- Inhaled but rarely multiply in IMMUNOCOMPETENT host
- If IMMUNOSUPPRESSED → Multiply → alveolocapillary blockage and decreased gas exchange → thickened alveolar septa
* Organisms rarely invade the parenchyma and are rarely found in alveolar macrophages
Which breeds are predisposed to Pneumocystis carinii?
- Mini (long-haired red) daschunds <1 year → can have a common variable immunodeficiency → absence of B cell + dysfunctional T cells
- Cavalier King Charles
How is Pneumocystis carinii definitely diagnosed?
- Lung biopsy or BAL
* Low globulins may also be present on bloodwork if common variable immunodeficiency is present
How is Pneumocystis carinii treated?
TMS
- more effective and less toxic than pentamidine
AZOLES ARE NOT EFFECTIVE
If a patient is diagnosed with Pneumocystis carinii what else should you look for?
Immunodysfunction
Where are pythium and lagenidium located geographically?
SE US
What is the infective form of pythiosis?
Motile biflagellate zoospore
*Encysts in damaged skin or GI mucosa
Pythiosis affects which layers of the GI tract?
Submucosal or muscular
How are oomycetes different from true fungi?
- Pythiosis and Lagenidiosis
1. Produce motile, flagellate zoospores
2. Have cell walls that lack chitin
3. Cell membranes LACK ergosterol
What segments of the GI tract are most commonly affected by pythium?
- Gastric outflow region
- Proximal duodenum
- Iliocecocolic junction
Cytology and histopathology of pythium and lagenidium often reveal what kind of inflammation?
Eosinophilic and pyogranulomatous inflammation
What are the best diagnostic tools for pythium?
- ELISA for serum antibodies → indicates active infection, high Sens and spec
- Can be used to monitor response to treatment - Culture → most successful from biopsy specimen
How can response to treatment be monitored in pythium patients?
ELISA for serum antibodies
What are the most common clinical signs associated with lagenidium?
Progressive cutaneous and subcutaneous lesions → typically ulcerated and edematous
(Pythium/Lagenidium) can cause rupture of the great vessels
Lagenidium
Serology for lagenidium will cross react with which other disease process?
Pythium
(Pythium/Lagenidium/Both) can be observed with a GMS stain
Both
(Pythium/Lagenidium/Both) can be observed on an H&E stain
Lagenidium
What is the preferred treatments for lagenidium and pythium?
- Aggressive surgical resection
2. Itraconazole and terbinafine post-op to help prevent recurrence
In pythiosis, complete resection should result in what % drop in ELISA?
50% in 3 months
Salmonella: Gram (+/-)
Gram -
What % of dogs with salmonella are asymptomatic carriers? Cats?
- 30%
2. 18%
When does clinically significant disease with salmonella occur?
Young, parasitized, immunocompromised animals
What are the possible outcomes after salmonella infection?
- Asymptomatic carriage
- Gastroenteritis
- Bacteremia/Septicemia
When should salmonella infections be treated?
When clinical signs appear. Should not be treated if healthy.
What is a good starting choice for antibiotics for salmonella?
Fluoroquinolones
What is the most globally widespread zoonotic disease?
Leptospirosis
What is the most prominent leptospirosis serovar in the US today?
- Grippotyphosa
- Icterohemorrhagic and canicola were most prominent prior to 1960
Where are the following leptospirosis serovars located geographically?
- Grippotyphosa
- Pomona
- East of the Mississippi
2. Northeast
Which leptospirosis serovars commonly cause
- Liver signs
- Renal failure
- Icterohemorrhagica and grippotyphosa
2. Grippotyphosa and pomona
What is the most common means of leptospirosis spread?
Water contact
What is the maintenance host for leptospirosis?
Burrowing rodents
Which dog breed is at higher risk for leptospirosis?
German shepherd
Acute renal failure is recognized in what % of leptospirosis cases?
90%
How does leptospirosis cause acute renal failure?
Acute decrease in GFR due to swelling that impairs renal perfusion
Concurrent hepatic failure along with acute renal failure is observed in what % of leptospirosis cases?
10-20%
Why might PU/PD in the absence of azotemia occur in a dog with leptospirosis
Nephrogenic diabetes insipidus secondary to lepto antigen
When do vaccinal titers for leptospirosis start to wane?
3-4 months after vaccination
As antibody concentrations increase, leptospirosis is cleared from most tissues except ____
Kidneys
*This is why the host can shed from kidneys for months to years after clinical recovery
What is the most common test for leptospirosis antibodies?
Microscopic agglutination test
MAT titers of ___ are supportive of a leptospirosis diagnosis but _____ is preferred.
- 1:800
2. Fourfold rise in titer over a 2-4 week interval
Which immunoglobulin increases first in leptospirosis infection?
IgM → rises in the first week (before MAT titers) and peaks in 14 days
- IgG becomes positive in 2-3 weeks after infection and peaks at 1 month
A single IgG/IgM test is suitable to distinguish between natural vs vaccine for leptospirosis because vaccinated dogs should have high ____ and low ___
- IgG
2. IgM
Which can identify the infective serovar for leptospirosis - MAT or PCR?
MAT
PCR for leptospirosis is (sensitive/specific) so you should only trust the (positive/negatives)
- Specific
2. Positives
Which antibiotic should be used to treat ill leptospirosis patients?
Ampicillin
*Eliminates the leptospiremic phase but does NOT eliminate the organism from the renal tubules
Once patients with leptospirosis are taking oral drugs or have recovered from ARF - which antibiotic should be used?
- Streptomycin - eliminate the leptospiruric phase
OR - Doxycycline - eliminates both the leptospiremic and leptospiruric phases
When should ciprofloxacin be used in the treatment of leptospirosis? Why?
- When meningitis or uveitis is observed
2. It crosses the blood brain barrier
What are negative prognostic factors for leptospirosis?
- German shepherd
2. Pomona serovar
What is the prognosis for leptospirosis?
50-80% survival
True/False: Giardia is zoonotic
True
How does giardia infect the host?
Ingested oocytes excyst in the upper SI and trophozoites attach to the intestinal mucosa from the duodenum to the ileum
Most giardia infections are (clinical/non-clinical)
Non-clinical
What are the options for diagnosing giardia?
- Trophozoites in duodenal juice or fresh fecal smear
- Oocysts on ZINC SULFATE float → shedding is intermittent
- Giardia antigen by fecal ELISA
How is giardia treated?
- Metronidazole for 5 days
2. Albendazole or Fenbendazole are also options (fenbendazole preferred because albendazole can cause BM suppression)
What compounds can help clean the environment of giardia?
- Steam
2. Quaternary ammonium compounds
Actinomyces vs Nocardia:
- Partial acid fast staining
Nocardia
Actinomyces vs Nocardia
- Hard to culture
Actinomyces
- Nocardia is easy to culture
Actinomyces vs Nocardia:
- Long filamentous in DENSE mats
Actinomyces
- Nocardia is in LOOSE mats or individual
Actinomyces vs Nocardia:
- Present in adult hunting dogs
Actinomyces
Actinomyces vs Nocardia:
- Present in young dogs (<2 years)
Nocardia
Actinomyces vs Nocardia:
- Spread directly (typically plant foreign bodies)
Actinomyces
Actinomyces vs Nocardia:
- Spread hematogenously
Nocardia
Actinomyces vs Nocardia:
- High mortality
Nocardia
Actinomyces vs Nocardia
- Sulfur granules present
Actinomyces
- Sulfur granules variable for nocardia
Actinomyces vs Nocardia:
- Treat with penicillin
Actinomyces
- Nocardia has variable susceptibility to sulfonamides, tetracyclines, or aminoglycosides
Aflotoxicosis is caused by ___. Which is generated by metabolism by ____ and then conjugated with ____ by ____.
- 8,9 epoxide
- Cytochrome p450 enzymes
- Glutathione
- Phase II enzymes
8,9 epoxide is (highly/minimally) lipophilic and is absorbed completely in the duodenum
- Highly
What is the mechanism of pathogenesis for 8,9 epoxide?
- Binds to other molecules in the cell leading to DNA adducts.
- Causes renal tubular and hepatic necrosis
What is another possible differential for aflotoxicosis?
Leptospirosis
What are the consequences of aflotoxicosis for patients that survive?
Fibrosis
How is aflotoxicosis treated?
- Various liver protectants
2. Oltipraz → inhibits phase I enzymes (CYP1A2) and induces phase I enzymes including glutathione
What is the causative agent of feline infectious peritonitis?
Feline corona virus → enveloped ssRNA virus
The majority of cats infected with feline corona virus (will/will not) develop FIP
Will not
- Only 1/10 will develop FIP
How soon is feline coronavirus shed in feces following infection?
2 days
When do most cats clear feline coronavirus infections?
After 2-3 months of fecal shedding
The following may associated with what disease process?
- Rising FeCoV titers
- Polyclonal gammopathy
- a1-acid glycoprotein
Feline infectious peritonitis
How is FIP definitively diagnosed?
IHC to demonstrate presence of FCoV virus in lesions (pyogranuloma, area of vasculitis)
Leptospirosis PCR has (high/low) Sens and spec?
Sens: Low
Spec: High
Feline infectious peritonitis: Effusive vs Non-effusive forms
- Antibody mediated immunity vs Cell mediated immunity
- Immune reaction type
Effusive: Strong AMI, Weak CMI, Type III
Non-Effuse: Strong AMI, Adequate CMI, Type IV
FIP ascites is caused by what?
Infected monocytes producing VEGF
What is antibody enhanced disease in the context of FIP?
If a FCoV + cat is vaccinated, it is more likely to have the effusive form of the disease and die from the disease - does not make a difference in a FCoV - cat
What is the gold standard for FCoV testing?
IFAT
What precautions should be taken if a cat has FCoV antibodies?
DO NOT STRESS THEM
How is pythium infection acquired?
Skin inoculation
Cryptosporidium vs Giardia
Site of infection: Primarily jejunum
Cryptosporidium
Cryptosporidium vs Giardia
Site of infection: Primarily small intestine
Giardia
Cryptosporidium vs Giardia
Trophozoites attach to brush border of GI epithelium
Giardia
Cryptosporidium vs Giardia
Type II merozoites attach to GI epithelium
Cryptosporidium
Cryptosporidium vs Giardia
Very small, require oil immersion microscopy for diagnosis
Cryptosporidium
What is required for 95% sensitivity in testing for giardia on zinc sulfate floats?
Need to perform at least 3 floats
What is the preferred method of giardia diagnosis?
Fecal ELISA - detects antigen
Cryptosporidium vs Giardia
Treated with paromyocin or nitazoxanide
Cryptosporidium
Cryptosporidium vs Giardia
Treated with metronidazole or fenbendazole
Giardia
Cryptosporidium vs Giardia
Oocysts can survive in the environment for months
Cryptosporidium
Cryptosporidium vs Giardia
Can be removed from the environment with quaternary ammonium compounds
Giardia
Cryptosporidium vs Giardia
Which is enteroinvasive?
NEITHER!
- They are found on the surface of the enterocytes and pathogenesis is not likely due to direct cellular damage.
Cryptococcus can be identified by which stain?
India ink stain
What test is preferred for cryptococcus diagnosis? What does it detect?
Latex agglutination test → detects capsular antigen
- Antibody titers are not useful due to the thick capsule keeping the body from producing a strong humoral response
What are sequelae that may result from canine distemper virus infection?
- Hyperkeratosis → paw pads and nasal planum
- Acute encephalomyelitis → occurs not long after infection
- Chronic distemper encephalitis → neurologic signs in older dogs that do not have a history of distemper infection
- Thymic atrophy → post-mortem finding in puppies
Where is canine distemper virus antigen found in dogs with hyperkeratosis?
Stratum spinosum and stratum granulosum
What should be ruled out before a diagnosis of distemper can be made in dogs with hyperkeratosis?
- Familial footpad keratosis → Irish terriers and Dogue de Bourdeaux
- Zinc responsive dermatitis → Huskies and Alaskan malamute
Dogs with chronic distemper encephalitis are (infectious/non-infectious)
Non-infectious
What is a post-mortem finding that can be found in puppies that had distemper virus?
Thymic atrophy
What is the organism?
- Zoonotic
- Found in 50% of puppies and 100% of kennels
- Causes voluminous watery diarrhea
- Zinc sulfate float often needed for diagnosis
- Treated with metronidazole
Giardia
What is the organism?
- Causes yellow, watery diarrhea
- Difficult to diagnose
- Zoonotic: Kills ~10% of AIDS patients
- Treatment is primarily supportive therapy
Cryptosporidium sp.
What is the organism?
- Occasional cause of diarrhea and death via colitis/enteritis
- Treatment is TMS and supportive care (albon also approved)
Coccidiosis
Toxoplasma gondii is excreted in the feces as a (sporulated/unsporulated) oocyst
Unsporulated
How long does it take for unsporulated Toxoplasma oocysts to sporulate?
Sporulated in 1-5 days but can survive in the environment for over 1 year
Toxoplasma gondii (Tachyzoites/Bradyzoites) replicate in intestinal walls
Tachyzoites
Toxoplasma gondii
(Tachyzoites/Bradyzoites) encyst in tissue
Bradyzoites
*Will encyst in tissue for the life of the host
Toxoplasma gondii
(Tachyzoites/Bradyzoites) can be the cause of reactivated infection such as after immunosuppression or can be a cause of chronic uveitis in cats
Bradyzoites
What is a unique feature for cats in the context of toxoplasma gondii?
They are the only species that can complete the life cycle and pass RESISTANT oocytes in feces
What is a consequence of immunocomprised cats being infected with toxoplasma gondii?
- They can have FATAL DISSEMINATION and intracellular replication of tachyzoites
- They can have transmammary infection as well
What tissues are most commonly affected in cats with disseminated toxoplasma gondii?
- Hepatic
- Pulmonary
- CNS
- Pancreatic
How does toxoplasma gondii infection occur?
- Ingestion of sporozoites, tachyzoites, or bradyzoites in most warm blooded vertebrates
- Transplacental is possible in most species → tachyzoites to fetus
- Transmammary is possible in cats
Which cats develop the worst clinical signs from toxoplasma gondii?
Kittens that were infected transplacentally or transmammary
- Generally die of hepatic disease or pulmonary disease
What is one of the most common causes of feline infectious uveitis?
Toxoplasma gondii
Toxoplasma gondii is (commonly/rarely) associated with clinical disease in the dog
Rarely
What is the duration that most cats and dogs will be Ab + with toxoplasma gondii infection?
For life → no point in repeated serum Ab titers after disease manifestations have resolved
Toxoplasma gondii
90% of cats with clinical toxoplasmosis have an elevated ___
IgM
- Greater than 1:64 is positive
Toxoplasma gondii: IgG vs IgM
___ has a higher predictive value than ___
- IgM
2. IgG
Toxoplasma gondii:
Serology for IgM is indicative of what kind of infection?
Either early infection or recurrent infection
- Detectable 2-4 weeks after infection and resolves in 16 weeks
Toxoplasma gondii
Serology for IgG is indicative of what?
Indicates past exposure to toxoplasma
What % of cats with clinical toxoplasmosis will have an increased IgG
60%
Toxoplasma gondii is now correlated to what human diseases?
- Schizophrenia
2. Learning disabilities
What precautions should be taken by households with pregnant women and cats?
- Clean the litter box every 24 hours → will not allow toxoplasma gondii oocysts time to sporulate
When do cats shed toxoplasma gondii oocysts?
Days to weeks following their PRIMARY INFECTION → repeat shedding rarely occurs even if the cat relapses with immunosuppression
Most seropositive cats with toxoplasmosis (are/are not) shedding oocysts
Are not
- Those shedding oocysts are usually not seropositive yet
What is the treatment for toxoplasmosis?
Clindamycin or TMS
- Will not totally clear the body of the organism → recurrent disease is common
What is the definitive host of neospora?
The dog
What are the intermediate hosts for neospora?
- Cow
- Dog
- Sheep
- Goat
- Horse
How is neospora transmitted?
- Aborted fetus/placenta/raw meat ingested from intermediate host
- Encystment in muscle and shedding of oocysts in feces
- Intermediate host ingests feces
* Dogs and cows can also do transplacental or transmammary
What are the clinical signs of neospora in:
- Puppies <6 mo
- Dogs >6 mo
- Ascending LMN paralysis
2. LMN flaccid paralysis with meningitis, encephalomyelitis, and cerellaritis
What is the definitive diagnostic tool for neospora? What are other options?
- ID of tissue cysts is definitive
2. Serology best, fecal unrewarding
What is the treatment for neospora?
Clindamycin for 4-6 weeks
What is the organism?
- Found in almost all puppies
- Zoonotic - visceral larval migrans
- Treated with Fenbendazole
Toxocara canis
How is toxocara canis treated?
Fenbendazole
What is the organism?
- Causes cerebrospinal nematodiasis
- Affects dogs
Baylisascaris
What is the organism?
- Zoonotic - creeping eruption cutaneous larval migrans
- Clinical effects due to blood loss (anemia, melena)
- Treated with fenbendazole
Hookworms
Ancylostoma, Uncinaria spp
How are hookworms (ancylostoma, uncinaria) treated?
Fenbendazole
What is the organism?
- Difficult to diagnose due to few eggs and intermittent shedding
- Bloody diarrhea, tenesmus
- Diagnose based on response to treatment
- Treated with fenbendazole
Whipworms
Trichuris vulpis
How are whipworms (trichuris vulpis) treated?
Fenbendazole
Where do dirofilaria immitis live in teh body?
Right ventricle and pulmonary arteries
Which rickettsial organism is part of the disease process for dirofilaria immitis?
Wolbachia
How are dipylidium spp transmitted? Are they zoonotic?
- Flea ingestion
2. yes
How are dipylidium spp treated?
Tapeworms
Droncit (praziquantel)
How are Taenia spp treated?
Tapeworms
Droncit (praziquantel)
Are Taenia spp zoonotic?
Yes
What are the results of intermediate host and definitive host infection of Taenia spp. in humans?
IH: Neural cystocercosis can lead to epilepsy
DH: Intestinal tapeworm from uncooked pork
What does the larval form of echinococcus granulosus cause?
Hydatid cysts in the brain, anaphylaxis
Which is more severe Echinococcus granulosos or Echinococcus multilocularis infection?
Multilocularis
What is Echinococcus multilocularis infection often thought to be?
Metastatic cancer → can cause multiloculated, thin walled, invasive cysts
What is the treatment for echinococcus spp?
Droncit (praziquantel)
How is rabies definitively diagnosed?
Direct immunoflourescence in brain tissue
What kind of virus is rabies?
Single stranded RNA lyssavirus
E. coli: Gram (+/-)
-
E. coli: anaerobic or aerobic
Facultative anaerobe
Salmonella: anaerobic or aerobic
Facultative anaerobe
What are the pathogenic forms of E. coli?
- ETEC → adheres and produces toxins (but doesn’t invade)
- EIEC → invades, replicates, and destroys epithelial cells
- EPEC → (not invasive or toxigenic) but attach and efface the brush border of enterocytes
- EHEC → produces verocytdtoxins that induce hemorrhagic ileitis and colitis
- EAEC → induce enterocyte pathology
Is salmonella enteroinvasive?
Yes
Where does rotavirus infect?
The villous tip in the intestine and causes sloughing and villous atrophy
Giardia, Crypto, Toxo: Large or small bowel diarrhea
Small
E. histolitica, T. foutus: Large or small bowel diarrhea
Large
What kind of virus is feline panleukopenia virus?
Small NONENVELOPED single stranded DNA virus
Feline panleukopenia is characterized by ___ and ___ with a (high/low) mortality
- Enteritis and panleukopenia
2. High
Feline panleukopenia virus has an affinity for what kind of cell?
Rapidly dividing (lymphoid, bone marrow, and crypt epithelium)
Feline panleukopenia is more sever in what kind of cat?
Young kittens
Feline panleukopenia virus - what is the consequence of infection at the following points in pregnancy?
- Early
- Middle 3rd to immediately post-natally
- Fetal death and resorption
2. Cerebellar hypoplasia