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ProTozoA Primer Cyst: infectious form of many protozoan parasites during which they are encapsulated inside a protective wall; usually found in the feces Cystozoites: encysted stages of certain coccidia that are found in paratenic hosts; when ingested, the cystozoite continues its development in the definitive host oocyst: encysted, highly resistant zygotic stage of some sporozoan parasites that may remain infective for extended periods of time sporulated oocyst: an oocyst that has developed into the infective stage in the environment trophozoite: active, motile feeding stage of the flagellate protozoa as well as the postsporozoite state that is seen in some apicomplexan parasites trypanosome: a flagellated protozoan found in the vascular system of definitive hosts Definitive host: host in which parasites reproduce sexually Intermediate host: host that harbors the parasite for a short transition period, during which (usually) some developmental stage is completed Paratenic host: host that is not necessary for the development of a parasite, but may maintain its life cycle aPPlICatIoNs to ClINICal PraCtICe Feline protozoan parasites are common yet potentially dangerous— both to cats and humans. Identifying whether cats are at risk for protozoan disease and preventing these disFigure 6. Trophozoite eases helps achieve better clinical of Tritrichomonas blagburni on direct outcomes and happy owners. smear of feces 1. Keeping cats indoors prevents exposure to outdoor threats since parasites and contaminated feces are sources of infection. 2. Preventing cats from hunting avoids exposure to infected prey; prevention includes safely eliminating rodents within the home. 3. Applying tick preventive to cats that are outdoors or exposed to other animals keeps them free from these vectors; consider year-round prevention. 4. Protecting kittens and immunocompromised cats by limiting their exposure to other cats, animals, and the outdoors greatly reduces risk for infection. trichomonads Tritrichomonas blagburni (= T foetus) and Pentatrichomonas hominis are relatively common infections in cats, especially in those housed together in catteries or shelters. T blagburni has not been found in human hosts; P hominis is known to infect humans, making transmission between humans and cats a possibility. Turn to Journal Club on page 79 to learn more about the recently named T blagburni organism. Transmission. Protozoa transmission occurs through ingestion of trophozoites from fecal-contaminated food or water. Clinical Signs. Recent research provides substantial supporting evidence that T blagburni can be a primary pathogen responsible for feline diarrhea. Previously, it was unclear whether it was directly responsible for this sign in cats.10 Diagnosis. Diagnosis can be made by: • Trophozoite observation on direct saline fecal smear (Figure 6) • Fecal polymerase chain reaction (PCR) • Fecal culture. Treatment. There is no approved treatment for cats, but ronidazole (30–50 mg/kg PO Q 12 H for 14 days) is the drug of choice. As previously mentioned, dietary management can also be helpful in resolving diarrhea. tvpjournal.com November/December 2013 Today's Veterinary Practice 77 Feline ProTozoa: recommendaTions From The comPanion animal ParasiTe council ParasiTe ProTocols |