• Abstract and Figures
• Public Full-text

P e r s p e c t i n A Newsletter fo r Cat Fanciers O n C a t s From The Cornell Feline Health Center Spring 1983 I I Feline Toxoplasm osis: The Disease and its Public H ealth Significance Sandy Baldwin, D.V.M., M.S. Though the parasitic disease toxoplasmosis In the entero-epithelial phase of is most often mentioned in connection with infection, the cat swallows the infective cats, in reality it is found in virtually organism, either from contaminated meat or all species of warm-blooded animals from sporulated oocysts previously passed throughout the world. Statistics show in feces. These oocysts then release that anywhere from 20% to 80% of all their organisms and infect the epithelial domestic animals in the United States have cells of the intestine. Following repro­ been infected at one time or another. It duction, oocysts (encysted organisms which has also been estimated that about half of are then passed in the feces) are formed. all people in this country harbor the Depending on the source of the infection, organism without showing any signs of oocysts can be detected in the cat's feces disease. The causative agent is an in 5 to 21 days. The oocysts will be intestinal protozoan, Toxoplasma gondii. passed daily for approximately 2 weeks, and there is the potential for passing Cats usually become infected in one of millions of oocysts in each bowel move­ two ways: 1) via ingestion of meat contam­ ment. After this 2-week period, oocyst inated with the parasite (either animals shedding stops, generally due to the caught in the wild or commercially pur­ development of immunity to the Toxoplasma chased meats); or 2) via ingestion of the organism by the host. sporulated oocysts (encysted organisms) after they have been passed in the feces The second, or systemic phase, occurs of another cat. There has been a recent at the same time as the intestinal stage. report of possible transplacental trans­ In this phase, organisms ingested by mission in cats. To understand the susceptible mammals (including humans) can differences in the two usual modes of localize in the intestinal epithelium or infection, the life cycle of the parasite spread rapidly throughout the body, caus­ will be discussed briefly. ing acute disease. As antibodies form, the Toxoplasma organism enters a resting Life Cycle stage and becomes encysted, that is, it becomes enclosed in a protective sac. There are essentially two phases of the This encystment is particularly apparent parasite: the entero-epithelial (intestin­ in the brain, heart, and muscles. These al) and the systemic phases. To date, tissue cysts are long-lived organisms and only the feline species has been recog­ are highly infective if the tissue is nized as a definitive host for Toxoplasma; consumed by another animal. Probably the in other words, only within the cat can major source of infection in cats is raw the organism undergo both phases; thus, meat infected with cysts; this may be from cysts are produced only in the cat and captured prey (rodents and birds) or raw serve as a source of infection for other meat fed by the owner. Cats fed homemade animals, including man. diets that include raw meats, such as Perspectives O n C a t s liver, may easily become infected. In As mentioned already, the production of man, the main source of infection is also antibodies correlates well with cessation most likely ingestion of raw or under­ of oocyst shedding in feces. There may be cooked meat, not contact with cats. numerous reinfections, but rarely is disease manifested after the first Clinical Disease and Immunity in Cats infection, due to protective immunity. However, feline leukemia virus is known to In general, a vast majority of cats that suppress the cat's ability to form anti­ become infected with Toxoplasma gondii bodies and if a cat has this virus, the never show any signs of disease. The only possibility of severely acute toxoplasmo­ indication that infection has occurred sis or resurgence of chronic infection is might be the demonstration of oocysts on a something always considered by your routine fecal examination and perhaps a veterinarian. slight rise in antibody formation in the blood serum. Very rarely there might be Diagnosis and Treatment mucoid or bloody diarrhea if a significant portion of the intestine becomes infected. If the cat is newly infected and passing This would probably have to follow the oocysts, diagnosis is usually straight­ ingestion of a massive number of oocysts forward. The oocysts are easily seen on or cysts in infected meats. When seen, fecal examination by your veterinarian. clinical disease is often in the young, The problem occurs if the cat is examined and can be severe to fatal. after the time fecal oocyst shedding has stopped. Blood tests will tell whether or not the cat has been infected previously. If acute disease does occur, pneumonia Because antibody levels to Toxoplasma rise is the most consistent sign. Fever, slowly, however, it is possible although labored breathing (from the pneumonia), unlikely that no antibody will be detected hepatitis, upper respiratory infection, in an early infection. Once a diagnosis and muscle inflammation (including the is made, treatment is available which heart) are other reported signs. Usually these resolve, and a strong immunity (Continued on ‘page 5.) develops. In old cats, whose general immunity is not as strong, small nodules may occur in the intestine and lead to intestinal obstruction. Perspectives A Newsletter for Cat Fanciers Very rarely, chronic disease can be On C ats From The Cornell Feline Health Center seen. It is usually manifested by 1) ocular disease involving any or all parts of the eye, 2) anemia, and 3) encephal­ The ultimate purpose of the Cornell Feline Health Center is to itis. Due to the nature and duration of improve the health of cats everywhere, by developing methods to prevent or cure feline diseases, and by providing continuing educa­ chronic disease, oocysts have long ceased tion to veterinarians and cat owners. All contributions are tax- to be shed in the stool. An unusual deductible. complication occurs if, for some unknown Director: Fredric W. Scott, D.V.M., Ph.D. reason, one of the tissue cysts ruptures, Asst. Director-Puhlic Affairs: Edna H. Federer Editor: Joyce Tumbelston releasing the organism, rapidly eliciting Secretary: Sheryl A. Bronger a severe allergic response. This most Special Consultant: Leo A. Wuori, D.V.M. commonly occurs in the areas mentioned ®1983 by the Cornell Feline Health Center, Cornell University, College of Veterinary before for encystment, namely the brain, Medicine, Ithaca, NY 14853. All rights heart, and muscle. The local tissue death reserved. Permission to reprint selected portions must be obtained in writing. Cornell that occurs will produce a myriad of signs University is an equal opportunity, affirma­ which vary with the site and in the amount tive action educator and employer. of tissue destruction. 3 A Message From the Director Fredric W. Scott, D.V.M., Ph.D. My last column contained the Cornell Feline I would like to take this opportunity to Health Center "Christmas Wish List." The thank Dr. Wuori for his valuable contributions response from our readers proved to me once to the CFHC over the past two years. It has again that cat lovers are among the most loyal, been a critical period of growth for the CFHC. devoted, and generous people I have ever known, His efforts have been vital in our reorganiza­ when it comes to the welfare of their pets. tion and expansion to help the Feline Center Two couples in particular deserve special serve the needs of both veterinary profession­ recognition for their exceptional generosity. als and the cat-owning public. Mr. and Mrs. Ellice McDonald, Jr., of Mont- chanin, Delaware, provided the funds for an CFHC Staff Reorganized incubator for critically ill cats, an isolation Dr. Wuori's retirement necessitated a restruc­ unit for raising germ-free kittens, and a turing of our office staff. Mrs. Edna Federer gradient mixer to aid the study of feline has been promoted to the position of Assistant viruses. A short time later, a large gift Director for Public Affairs. She is responsi­ (also intended for the purchase of a gradient ble for the day-to-day operations of the mixer) arrived from Don and Joan Blackburn of office, fund raising, publications, continuing San Antonio, Texas. With their permission, education, and coordinating the activities of their gift will be applied to the purchase of an external volunteer organization currently another equally important item used for study­ being formed. Her advancement from Secretary ing feline viruses. to Administrative Aide to Assistant Director As you might imagine, there was great reflects her outstanding abilities and total elation at the Feline Health Center when these dedication to the Feline Health Center and its gifts arrived. The warm-hearted response to goals. our needs truly surpassed our expectations. I Mrs. Joyce Tumbelston, Assistant Editor for cannot overstate the beneficial effect these the past two years, now assumes the duties of gifts will have on cats. Once again, I'd like Editor. A very talented individual, Joyce has to express our deepest gratitude to the done an extraordinary job with our publica­ McDonalds, the Blackburns, and each one of you tions, given the limited help and resources who sent a gift to help meet these needs. available to her. Our publications and commun­ ications with practicing veterinarians and cat Dr. Leo Wuori Retires owners are the lifeblood of the CFHC; without As of January 1, 1983, Dr. Leo A.

Load more

  8

Copy Link