Miscellaneous Infections Flashcards
T/F: Dogs do not produce Toxoplasma gondii oocysts but they can mechanically transmit oocysts after they ingest feline feces.
TRUE
What does the serologic assay detect in cases of Neosporosis: antibody or antigen?
antibody
What is a potential complication of long-term treatment with allopurinol for Leishmaniosis?
xanthine urolithiasis
What is the mechanism of action of miltefosine against Leishmania spp.?
activates proteases in Leishmania spp. and causes apoptotic death of the parasite
Mode of transmission of Protothecosis
cutaneous inoculation of organisms into tissues; systemic invasion in the face of immunosuppression from organisms ingested or colonize the intestinal tract
What breed(s) of dog is predisposed to Protothecosis?
Boxers and Collies
What type of immunity is needed to successfully clear Leishmania spp.?
Th1-cell-mediated immune response; production of cytokes such as IFN-gamma and TNF-alpha activate macrophages to destroy amastigotes through nitric-oxide mediated mechanisms
Histopathological findings with Toxoplasmosis
Pyogranulomatou inflammation with necrosis - T. gondii tachyzoites or bradyzoites may be detected - DNA can be amplified from tissue
What breed of dog has been reported to have Leishmaniosis in the United States?
Foxhound
How do Prototheca spp. reproduce?
endosporulation
Treatment of choice for Neosporosis
Clindamycin, other reported treatments include TMS, pyrimethamine, ponazuril
What prevention strategies are recommended for Leishmaniosis?
use of ectoparasiticides that repel sandflies (such as permethrins); keeping animals indoors from dusk to dawn (when sandflies feed); dopamine-based oral suspension Leisguard –> activates phagocytic cells and enhances intracellular killing of the parasite; vaccination with purified excreted-secreted proteins of Leishmania infantum (CaniLeish)
Mechanism of action of amphotericin B against Leishmania spp.?
binds to ergosterol in the protozoal membrane and blocks the ability of Leishmania spp. to enter macrophages
Two major life cycle forms of Leishmania
promastigote and amastigote
Causative organism of Leishmaniosis
Leishmania infantum (major); Leishmania braziliensis (American tegumentary leishmaniosis)
Diagnostic approach for Toxoplasmosis
Demonstration of serum antibodies that suggest exposure to Toxoplasma gondii; IgM titer higher than 1:64 or a 4-fold or greater rise in IgG titer - suggest recent or active infection; Clinical signs of disease consistent with toxoplasmosis; Exclusion of other common causes of the clinical syndrome; positive response to appropriate treatment
Why might an animal have a false negative serologic test for Leishmania spp.?
may reflect delayed seroconversion in some animals - which can take several months to occur
What is the primary reservoir for Leishmania infantum?
dogs
Diagnostics available for leishmaniosis
1) Cytology of affected lesions – identification of Leishmania amastigotes is diagnostic; 2) Histopathology of affected lesions; 3) Serology (immunofluorescent antibody); 4) PCR; 5) Culture
T/F: Neospora caninum poses a serious human health risk.
False - DNA of N. caninum has never been found in humans
Major Clinical signs associated with Leishmaniosis
Weight loss, anorexia, scaling and/or ulcerative cutaneous lesions, onchogryphosis, fever, keratoconjunctivitis, uveitis, lymphadenopathy, hepatosplenomegaly, pallor, lameness, renal failure
What are the possible outcomes after infection with Leishmania?
1) complete elimination of infection, 2) subclinical infection, 3) severe, life-threatening disease
Treatment options for Toxoplasmosis
Clindamycin, TMS, Azithromycin, Ponazuril
T/F: Positive serum antibodies to Toxoplasma gondii indicate active infection.
True - it is likely that most animals harbor tissue cysts for life
Describe the life cycle of Toxoplasma gondii
Cats ingest bradyzoite cysts in tissues of prey –> bradyzoites transform into merozoites & undergo schizogony in GI tract –> produces a zygote –> shed as an unsporulated oocyst in the feces –> sporulation occurs within 1-5 days; Sporozoites penetrate intestinal cells and transform into tachyzoites
What is the characteristic morphologic form of Prototheca spp.?
morula – internal septation os spherules into multiple endospores results in a wheel-like or daisy-like appearance
Why might an animal have a false positive imunofluorescent antibody test for Leishmania spp.?
cross-reaction with antibodies to Trypanosoma spp. or previous vaccination for Leishmania
Where is the promastigote of Leishmania found?
gut of the sandfly vector
What is the clinical lesion associated with American tegumentary leishmaniosis?
nodular skin lesion at the site of the sandfly bite
Major Clinical signs associated with Toxoplasmosis?
cats: fever, ocular inflammation, ataxia, seizures, muscle pain, respiratory distress; dogs: similar signs but develop illness less frequently than cats
What happens when cattle ingest sporulated oocysts of Neopsora caninum?
can lead to transplacental spread of tachyzoites and abortion
Mechanism of action of allopurinol against Leishmania spp.?
interferes with protein synthesis by Leishmania spp.
Major Clinical signs associated with Protothecosis?
cutaneous nodules or masses; systemic illness with weight loss, blindness (ocular involvement), PU/PD, hematochezia***, vomiting, lameness, neurologic signs
Mode of transmission of Neospora caninum
dogs can be infected transplacentally or through transmammary route; postnatally, dogs may be infected after they ingest infected tissues of intermediate hosts or bovine fetal membranes
What is the causative agent of Protothecosis?
Prototheca spp. - Prototheca wickerhamii has been isolated from cutaneous infections, unicellular algae – lack chlorophyll, dependent on a saprophytic lifestyle
Geographic distribution of Leishmaniosis
primarily southern Europe, Middle East, Central and South America; some parts of the USA
What breed of dog is resistant to clinical disease of Leishmaniosis?
Ibizan hound
Skin lesions associated with leishmaniosis
scaling, crusting, hyperkeratosis, alopecia, erythema, cutaneous ulceration - most often occurs on limbs, pinnae, muzzle, periocular region
Only cats can complete the sexual phase of what parasite in their intestinal tract, resulting in passage of oocysts in the feces?
Toxoplasma gondii
Major Clinical signs associated with Neosporosis?
Ascending paralysis, muscle atrophy, neurologic (cerebellar) signs, nodular dermatitis, respiratory distress
Histopathological findings with Neosporosis
pyogranulomatous inflammation and tachyzoites
Cytological characteristics of Prototheca spp.
pyogranulomatous to granulomatous inflammation with numerous intracellular spherules that are round, oval, or polyhedral (nonbudding)
Describe the life cycle of Neospora caninum
Dogs become infected when they ingest tissue cysts in bovine placental material –> bradyzoites are released in intestine –> transform into merozoites –> zygote forms and is shed in feces as unsporulated oocyst –> organisms can also penetrate the dog’s intestinal tract and form tissue cysts (reactivation of these cysts in pregnancy can result in repeated transplacental transmission to fetus)
Describe the life cycle of Leishmania infantum
Animal is bitten by an infected sandfly –> promastigotes are inoculated into dermis and penetrate macrophages –> within the macrophage, they transform into amastigotes and replicate within a phagolysosome –> macrophage ruptures and new macrophages are infected –> infected macrophages disseminate via regional lymphatics and blood to infect reticuloendothelial system –> amastigotes are ingested by female sandfly during feeding and convert back to promastigotes –> replication completes the life cycle
Cytological characteristics of Neospora caninum
tachyzoites can be visualized in aspirates of skin lesions – 6x1 um and oval to crescent-shaped
vectors for transmission of Leishmaniosis
Phlebotomus (Old World) and Lutzomyia (New World) sandflies
What is the primary reservoir for Leishmania donovani?
humans
Treatment of choice for Leishmaniosis
Combination of meglumine antimoniate (for 4 weeks) and allopurinol until clinical signs have resolved and quantitative serology becomes negative
What are treatment options for Leishmania spp. besides meglumine antimoniate and allopurinol (treatment of choice)?
miltefosine; amphotericin B; ketoconazole; aminosidine (aminoglycoside); marbofloxacin
What is the definitive host of Neospora caninum?
domestic dogs and wild canids (coyotes, dingos, wolves)
Meglumine antimoniate is derived from what substance?
antimony
Treatment of choice for Protothecosis
surgical excision, amphotericin B and itraconazole, alternative drugs include aminoglycosides or tetracyclines
T/F: Cats are relatively resistant to leishmaniosis.
TRUE
Mechanism of action of meglumine antimoniate against Leishmania spp.?
inhibit protozoal enzymes and damage protozoal DNA
Histopathological findings with Leishmaniosis
orthokeratotic to parakeratotic hyperkeratosis, acanthosis, ulceration, granulomatous to pyogranulomatous inflammation with variable numbers of intrahistiocytic amastigotes; destruction of the sebaceous glands in 45% of cases; variety of inflammatory patterns - most common are granulomatous perifolliculitis, superficial and deep perivascular dermatitis, interstitial dermatitis
Geographic distribution of Protothecosis
worldwide except Antartica, esp. in warm, humid climates and where there is organic matter with high water content
Histopathological findings with Protothecosis
nodular to diffuse, pyogranulomatous to granulomatous dermatitis and panniculitis with numerous fungal elements
