Exam3 Flashcards
Nematode Parasites of the Respiratory System
Morphology and Biology
- Small worms with superficial resemblance to hookworms
- Dioecious and sexually dimorphic
- Males rudimentary copulatory bursa
- Generally feed on host cellular tissue, not blood
- Most develop to infective stage in obligate intermediate host
Dog Lungworms
Filaroides hirthi
Filaroides osleri
Filaroides hirthi
- Adults in lung parenchyma
- PPP = ~35 days (5 wks) post infection
- L1 infective stage
Filaroides osleri
- Adults in trachea and bronchi
- Form nodules detectable @ 2 months
- PPP ~6-7 months post infection
Filaroides spp. Life Cycle
- L1 passed in feces of infected mother called COPROPHAGY: normal ingestion of feces by animals.
- Puppies infected by ingestion of L1. May be through ingestion of larvae in vomitus of mother.
- L1 ovoviviparous eggs hatch w/in uterus of adult female worms
- Tracheal migration by the hepatic circulation
Diagnosis
- Baermann exam
- Zinc sulfate flotation
- KINKED TAIL w/ DORSAL SPINE
- Larvae ~ 350um.
- Shed intermittently, collect feces for 5 days is best
- Active migration of live larvae out of feces to water and settle at the bottom stem of glass.
- Microscopic wet mount
Clinical significance
- Include hard, dry coughing
- Stimulated by cold air or exercise
- Chronic and unremarkable
- Possible obstruction of trachea
- At necropsy, focal areas of necrosis in the parenchyma of the lung lobes
- Severe disease in hyper infected and immunocompromised
Treatment and prevention
- Tx difficult with variable results
- Efficacious chemotherapy: cessation of symptoms, cessation of larval shedding, clinical improvement.
- FBZ SID (once daily) for 7 days resolved, but failed to remove worms SID for 14 days
- IVM 1000ug/kg twice = 74% effective
- 5-10% of treated dogs continue to shed larvae
- *Prevention by avoiding contact w/ infective larvae (easier said than done)
Angiostrongylus vasorum
French heartworm
- Small worms living in the right heart/pulmonary artery
- Widespread in Europe.
- Associated with pulmonary thrombosis, clotting disorders, hemorrhage from deposited eggs and larvae.
Treatment
- Milbemycin weekly (4x)
- Standard heartworm prophylactic dose
- Not zoonotic
Wildlife
-Incidental finding in Red Fox (Vulpes vulpes) from West Virginia
-Did not seem to be associated with significant pathology
Others: Angiocalus gubernaculatus.
Angiostrongylus costaricensis
- Living in mesenteric arteries
- Spread in Florida, deaths in primate colonies
Angiostrongylus cantonensis
- Associated with neurologic disease from larvae in meninges and inflammatory response
- Naturally occurring in rats in Southeast Asia
- Spread to North America (New Orleans). Fatal case Howler monkey in zoo.
- 1st human case in 1995
Zoonotic Angiostrongylus cantonensis
- Definitive host: RATS
- Intermediate host: Grasshopper
- L1 shed in feces. IH ingests L1
- L3 infective stage in the IH
- Incidental ingestion of gastropod larvae by humans via infected produce
Symptoms in TN
- Eosinophilic meningitis in infant
- Tx: ABZ w/ corticosteroids
Aleustrongylus abstrusus
Cat lungworm
Indirect life cycle
- L1 passed in feces ingested by snail/slug
- IH: snail, gastropods
- L3 infective stage in birds
- Paratenic host: Birds, mice
- PPP= 5-6 weeks
Pathogenesis
- Tiny worms parasitic in terminal bronchioles and alveolar ducts
- Eggs are laid in lung parenchyma
- “nests” of worms appear as small nodules w/ associated inflammatory response and focal necrosis
- coughed up and swallowed, then passed in feces.
Clinical significance
- Prevalent in free-ranging cats
- Often clinically in apparent and unremarkable
- Occasionally seen in routine fecal exams
- Coughing, dysorexia, cough, dyspnea, polypnea in severe cases.
- Fatal complication w/ anesthetic associated deaths in shelter-run spay/neuter program 9%
Diagnosis
- Fecal Bearmann exam
- Zinc sulfate flotation
- Larvae ~350um, kinked tail w/ dorsal spine
Treatment
- FBZ SID 3-15 days
- Prevention by reducing predation of paratenic host and infective larvae
Troglostongylus sp.
Lungworm
- Agent of feline respiratory disease in Europe and Mediterranean
- Indirect life cycle
- L3 infective stage in snail (IH)
- Various species occur in frontal sinuses, bronchi, and trachea of cats.
- Does not appear to occur in pet cats in USA
Capillaria spp.
- Small worm with whip-like anterior ends
- Parasites of all classes of vertebrates, reptiles, amphibians, birds, mammals.
Life cycle
- Variable
- simple direct
- Facultative indirect w/ paratenic host
- Obligate indirect w/ intermediate hosts
Species of veterinary importance
-Respiratory tract/sinuses
Capillaria (Eucoleus) boehmi, C. aerophilus
-Urinary tract
C. plica (Pearsononema), C. feliscati
-Alimentary tract/intestine
C. (Aonchotheca) puttori
Cat and Dog Lungworms
-Capillaria (Eucoleus) aerophila
Adults in bronchi
-Capillaria (Eucoleus) bohemia
Adults are in nasal sinuses
-Small worms (25 to 35mm)
Life Cycle
-Facultative indirect (earthworm as paratenic host)
Clinical signs
-Bronchopneumonia, rattling wheezy respiration, coughing, ADR.
Diagnosis by fecal flotation
- control by environmental hygiene
- successfully treated
- Macrocyclic lactones drugs
Lungworm parasites of Domestic Livestock
Muellerius capillaris
Metastrongyloidea
- Larvae, obligate indirect life cycle
- Tiny parasites deeply embedded in the respiratory tissue (parenchyma) of goats and sheep.
- L1 passed in feces
- L3 infective stage, tracheal migration to lungs
- Adults reproduce and begin passing larvae ~ 4 weeks Post infection
Clinical importance
- clinical symptoms result from heavy infections in immunocompromised animals
- Coughing and rapid breathing, weight loss, etc.
- 1st stage larvae easily differentiated from Dictyocaulus by kinked tail
- Macrocyclic lactone @ 200-500 um/kg
Lungworm parasites od Domestic Livestock
Dictyocaulus spp. (no kinked tail or dorsal spine)
Trichostrongyloidea
Direct life cycle
- Horse and donkey (D. arnfeldi)
- Cattle (D. viviparus)
- Sheep and goats (D. filaria)
- L1 passed in feces
- Bearmann test
- Infective stage in ~5days
- Ingested larvae migrates to lungs via mesenteric lymphatic nodes and thoracic duct
- Adults reproduce ~4 wks PI
Clinical sings
- light infections often asymptomatic
- Horses more susceptible than donkeys
- Heavy infections occlude airway and obstruct airflow.
- Decreased eating/weight gain resulting from stress to breathe
- Host resistance is function of age, vigor, genetics, established infection, acquired immunity
- Environmental conditions: moderate temperatures, damp pastures.
- Successful treatments with macrocyclic lactones
Metastrongylus sp.
Swine lung worm
- commercial confined operations not much of an occurrence
- free-range need to maintain awareness
Direct, Facultative indirect life cycle
- Most often in bronchioles and trachea
- Thread-like resembles hookworms
- 3 species
- Embryonated eggs passed in feces
- L3 infective stage (infected earthworm)
- Migrate to lung to reproduce
- PPP 25 days
Metastrongylus elongatus
- diagnosis by fecal flotation
- superficial resemblance to Ascaris suum (40x50 um)
- thick mamillated shell, single cell, larvated egg in feces or sputum.
Clinical significance
- Alveolitis/broncholitis
- Chronic and paroxysmal coughing
- Unthriftiness failure to meet ADG production goals
- Secondary pneumonia with dyspnea and abdominal respiration (thumps)
- Both parasitisms may occur in pasture contaminated with Ascaris and Metastrongylus
Control and prevention
- Prevent ingestion of paratenic/intermediate host
- nursing piglets may get larvae or eggs from sow
- FBZ effective
- Ivermectin, Doramectin ~21, 24 days
Heartworm Infection and Disease in Dogs
Dirofilaria immitis
Canine heartworm
Dirofilaria immitis
- Veriform embryonic stage called microfilaria
- Diagnostic for infection status
- Dogs infected by mosquitoes
- Mosquitoes harbor infective larvae
- The larvae migrates in SQ tissue, colonize pulmonary artery ~70-100 days PI and become reproducing adults
- Microfilariae begin circulating 6 months post infection
- PPP 6 months
- Female mosquitoes feeding on microfilaremic dogs complete the life cycle
- Development to infective stage in the mosquito ~ 14 days @>57F (L3)
- Transmission to new host (L4) infective to dog
- Worms live in pulmonary arteries and right side of heart
- Seasonal and perhaps year-round transmission
- Wild canids opportune reservoir
- TN top 10 state
Clinical signs
- Immune stimulation of host tissues by adult worms and their products. Obstructive fibrosis, pulmonary and endothelial damage, impaired blood flow, reduced cardiac output.
- Hypertension, hypertrophy, enlargement of the right side of heart. Reverse D radiograph profile. Pulmonary infiltrates
Microfilaria immitis
Pathogenesis
**The most significant veterinary health issue in companion animal medicine
-Kidney disease from obstruction of glomeruli
- Antigen-antibody complexes
- Microfilaria (embryonic stage, not larvae)
- Wolbachia pipientis (gram negative bacteria) endosymbiotic. Incites inflammation, present in arthropod vectors. Transmitted in utero from adult female worms to their microfilariae.
- Larvae pushes through right atrium and vena cava
- Interference of blood flow and AV valve
- Jaundice, hemoglobinemia and hemoglobinuria
- Fatal if not attended promptly
- Uncontrolled hemorrhaging
- Secondary host response triggered by various infectious disease events
- Heartworm induced pulmonary thromboembolism
Heartworm Preventatives
DEC: Diethyl Carbonamide
- DEC + Oxibendazole, extremely microfilarcidal
- Targets L3 at molt to L4
- Given by mouth SID
- Has plus for enteric nematode parasite control
- Anaphylactic shock**
Currently
Monthly administration
**Kills L3 and early L4 larvae acquired last 30 days since last treatment
- Heartguard: IVM, Pyrantel pamoate
- Sentinel: Milbemycin, Lefenuron
- Advantage multi: Moxidectin, Imidacloprid
- Trifexis: Mibemycin oxime, Spinosad
- Simparica Trio: Pyrantel, Moxidectin, Sarolaner
- Revolution: Seleamectin
Heartworm susceptibility to Macrocyclic lactone drugs
and Melarsomine dihydrochloride adulticide therapy
0-30 days: L3-L4 (susceptible)
30-80/120 days: Susceptiable gap
120-210 days: Melarsomine susceptible, Adult (antigen positive)
Emerging Drug Resistance
- Evidence monthly HW prophylaxis failure associated with over expression of the P-glycoprotein (aka MDR1) . Heartguard, Interceptor
- Prevents macrocyclic lactone from crossing BBB
- *Annual testing important
- *Mississippi Delta: high rates of transmission
Lack of Effectiveness, Gaps in Owner Compliance
-Geographic isolates known to over express P-gp w/LOE to HW preventative drugs
- Establish the HW status of all pets at least once a year. Antigen and microfilaria testing
- Discuss heartworm prevention at every visit
- Good compliance
- Poor compliance-Review risks
- Keep track of purchase history
- Online reminders
- *heartworm compliance tool: window of infection
