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What are the characteristics of cryptococcosis?
- Caused by: Cryptococcus neoformans or C. gatii, dimorphic, saprophytic, yeast-like fungus with narrow-based budding, thick polysaccharide capsule
- Transmission: C. neoformans associated with bird feces, C. gattii with Eucalyptus trees and koalas. Most cats and some dogs (esp Cocker spaniels) carry in nasal passages. Capsule is antiphagocytic and immunosuppressive.
- Pathogenesis: Nasal granulomas have local extension to CNS (brain and meninges), eyes, LNs, skin. Don't have to be immunocompromised
- CS in cats: Usually respiratory, CNS, ocular, or cutaneous involvement. Variable nasal involvement.
- CS in dogs: CNS and eyes, subclinical nasal cavity involvement. Widespread dissemination to parenchymal organs (pancreas, gastrointestinal tract, myocardium, kidneys, liver etc) which contrasts cats
- Dx: Nasal rads, CT scan, thrx rads (miliary nodular pattern), cytology, cryptococcal antigen latex agglutination test (LCAT, widely used, sensitive and specific test)
- Txt: fluconazole (CNS and urine penetration), itraconazole, Amphotericin B (SC to cats to prevent nephrotoxicity), flucytosine ($$$, synergistic with AMB), sx debulking. Treat until signs resolve and LCAT titer to 0
What are the characteristics of Sporotrichosis?
- Caused by: Sporothrix schenckii, dimorphic fungus found worldwide, round yeast in tissues
- Transmission: cats transmit the infection to humans
- Pathogenesis: cutaneous (multiple nodules that may ulcerate, most common form in cats, autoinoculation with grooming), cutaneolymphatic, disseminated. Should look just like crypto!
- Dx: cytology (numerous organisms in cats, hard to find in dogs, pleomorphic yeast in
- phagocytes or extracellularly)
- Txt: itraconazole is the drug of choice, for one month after all lesions resolve
- Px: good
- Prevention: wear disposable gloves, and wash with chlorhexidine or povidone-iodine if handling suspected cases
What are the characteristics of Giardiasis?
- Caused by: Giardia duodenalis, pear-shaped,binucleate motile trophozoite with four pairs of flagella. Subdivided as human (a, b), dogs (c, d), cats (e) so not really zoonotic
- Transmission: fecal-oral ingestion of cyst form containing two incompletely separated
- Who gets it: immunodeficient, young, and group-housed animals, esp dogs
- Pathogenesis: cysts ingested -> gastric acid causes excystation (duodenum) -> separation, maturation, attachment -> damage to microvilli, epithelial sloughing, villous blunting, toxin production -> maldigestion, malabsorption and encystation, shedding
- CS: most infections subclinical; malodorous, pale, and steatorrheic feces (increased fecal mucus in cats)
- Dx: ZnSO4 fecal float (cysts or trophozoites, falling leaf pattern) x3 in 3-5 days, direct immunofluorescence, PCR, Giardia antigen ELISA assays (recommended in combination with float)
- Txt: fenbendazole (very effective), metronidazole (less effective)
- Prevent: clean contaminated environment, address underlying gastrointestinal disease or immune deficiency
What are the characteristics of Trichomoniasis?
- Caused by: piriform flagellate with undulating membrane, ONLY has trophozoite (no cyst)
- Transmission: normal inhabitant of the large bowel (except Tritrich) so fecal-oral
- Who gets it: cats <1year old in multi-cat households get T. foetus
- CS: Acute to chronic, often intermittent, large bowel diarrhea with fresh blood and mucus. Anus swollen and erythematous, but cats usually otherwise healthy
- Dx: fecal wet mount for rolling motion, InPouch TF test for bovine T. foetus, PCR
- Txt: Ronidazole (watch for neurotoxicity), metronidazole and fenbendazole often ineffective, high fiber diets may help. Self limiting in months to years
What are the characteristics of coccidiosis?
- Caused by: Obligately intracellular parasite (phylum Apicomplexa). Isospora is the most common
- Who gets it: healthy dogs and cats, esp group-housed animals (indicator of poor sanitation). Signs most common in very young or immunosuppressed animals, and following stressors
- Transmission: ingestion of oocysts or tissue cysts in mice or other mammals
- Pathogenesis: unsporulated oocysts in feces, sporulate in 8 hours, ingested, 8 sporozoites per cyst infect GI epithelium, schizogony, sexual fertilization, unsporulated oocysts
- CS: Usually none, can be D
- Dx: fecal float
- Txt: TMS if have severe D
- Prevention: Good hygiene, discourage hunting and raw meat
What are the characteristics of cryptosporidium?
- Caused by: phylum Apicomplexa, family Cryptosporidiidae, 4-5 μm in diameter. C. parvum most common in mammals (infects dogs, cats and humans)
- Transmission: highly infectious, epitheliotrophic parasite, resistant to disinfectants, survive in environment for months. Esp in water (swimming pools), resp and GIT of birds, reptiles and mammals
- Pathogenesis: Oocysts ingested -> 4 sporozoites are released -> schizogony beneath the PM -> fertilization -> thick-walled oocysts which are shed sporulated in the feces or thin-walled oocysts which rupture in the lumen and release sporozoites = AUTOINFECTION. Shed for months
- CS: most are subclinical. Signs are severe, life-threatening D in immunosuppressed
- Dx: Fecal examination (look for oocysts, acid fast stain), direct fluorescent antibody (high sensitivity), PCR
- Txt: self-limiting (immunocompetent), no good txt but can try tylosin; treat underlying immunosuppression
- Prevention: steam cleaning, liberal use of boiling water. Warn owners of the risks to immunocompromised people; infections may be fatal
What are the characteristics of canine babesiosis?
- Caused by: RBC parasites B. canis (large pyriform organism, singly or paired in RBCs), B. gibsoni (small pleomorphic organism, found singly in RBCs), B. conradae
- Who gets it: feline babesiosis not documented in US. B. canis (kennels, adults, Greyhounds)
- Transmission: tick-borne (B. canis), blood transfusions (so screen!), fighting. B. canis vogeli vectored by Rhipicephalus sanguineus, B. canis canis by Dermacentor spp.
- Location: B. canis (gulf coast, south, central and southwestern US). B. gibsoni in OK, NC, AL, MN, IN, MO, esp in pitbulls in AL and subclinical. B. conradae in southern CA
- CS of B. canis: multiplication in RBCs by binary fission -> hemolysis, anemia, fever. Sometimes icterus, splenomegaly and IMTP. Chronic carrier state usually subclinical
- CS of B. gibsoni: fever, anorexia, weakness, anemia (pallor), thrombocytopenia (petechiae), organomegaly, lymphadenopathy. Icterus rare
- Dx: CBC (thrombocytopenia, regenerative anemia), Coombs test (+), serology (titers > 1:80 positive, rising titers suggest recent infection), PCR (current test of choice)
- Txt: Blood transfusion, IVF, antibabesial drugs (imidocarb diproprionate, atovaquone and azithromycin). No glucocorticoids.
- Prevention: tick control, avoid splenectomy and immunosuppression in chronically infected dogs, screen blood donors serologically
What are the characteristics of feline cytauxzoonosis?
- Caused by: Cytauxzoon felis
- Location: southern and SE US (MI, AR, OK, TX, MO, LO, FL and mid-Atlantic states)
- Who gets it: outdoor cats Apr-Sept
- Transmission: tick borne
- Pathogenesis: schizogonous phase of infected mononuclear phagocytes. Intraerythrocytic phase (ring shaped orgs seen in RBCs)
- CS: DIC, shock (schizont phase), hemolytic anemia (intra-RBC phase). Usually rapidly fatal with dark urine, dehydration, icterus, pallor, prolonged CRT, hypothermia. Some mild strains recently found
- Dx: CBC (NR anemia, leukopenia, thrombocytopenia), prolonged coagulation times, blood smear
- Txt: High mortality despite treatment. Supportive care, heparin?
- Px: usually (not always!) fatal
What are the characteristics of Toxoplasmosis?
- Caused by: obligate intracellular coccidian parasite, T. gondii
- Who gets it: definitive host Felidae
- Transmission: cats ingest bradyzoites in tissue cysts -> sexual replication to oocysts in feces -> ingested by intermediate host and forms tachyzoites and bradyzoites in tissue. Can also have transplacental/congenital (if naive, but won't reactivate bradyzoite cysts). Naive cats shed millions of oocysts per day, immune cats prevent sexual replication. Severe immune suppression can activate tissue bradyzoites
- CS: most infections subclinical. Cats can have stillbirth, anorexia, lymphadenopathy, fever, dyspnea, coughing, CNS signs, vomiting, diarrhea, icterus, abdominal effusion, pancreatitis, splenomegaly, myositis, uveitis, chorioretinitis. Dogs are like cats, but ocular disease less common and have chronic neuromuscular disease.
- Dx: cytology (not great), thrx rads (diffuse interstitial to alveolar pattern, pleural effusion), abd rads (lymphadenopathy, hepatomegaly, peritoneal effusion), fecal float (low sensitivity), serology (IgM >64), histopath (tachyzoites, NOT bradyzoite cysts), PCR
- Txt: supportive, drug of choice is clindamycin
- Prevent: 30% of dogs and cats seropositive in the US; pet cats of little risk except to seronegative pregnant women
What are the characteristics of neosporosis?
- Caused by: Neospora caninum, thick cyst wall
- Transmission: transplacental following ingestion of tissue cysts (in CNS, PNS, retina, muscle) by carnivores or oocysts by herbivores. Bitches reactivate during pregnancy (infects most pups)
- Who gets it: purebred dogs (especially farm dogs), cattle
- CS: herbivores (abortion), dogs (neuromuscular, so see ascending paralysis, muscle atrophy and stiffness in dogs <6 months="" of="" age="" br="">
- Dx: serology (IFA), PCR
- Txt: clindamycin, prednisone
- Prevention: limit access of dogs to raw meat and placental materials on farms
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