Toxic Tale of Toxoplasmosis in Cats

Dr A Sangaran
Dr ST Bino Sundar
Toxoplasmosis is one of the most common parasitic diseases and infects nearly all warm-blooded animals, including pets and humans. Know more about the infection and how you can take care of your feline.
 
It is a disease caused by the protozoa Toxoplasma gondii. When a cat ingests infected prey or raw meat, the parasite is released from cysts into the cat’s digestive tract, where it reproduces and produces oocysts. Infected cats then excrete these oocysts in their feces in millions. Newly exposed cats usually begin shedding oocysts 3 to 10 days after consuming infected tissue, and continue shedding for around 10 to 14 days.
 
Oocysts are very hardy and may survive in the environment for well over a year. Oocysts passed in the feces of cats are not immediately infectious to other animals. Before becoming infectious, they must go through a process called sporulation, which takes one to five days depending on environmental conditions. Cat feces containing sporulated oocysts, however, serve as sources of infection, regardless of whether they are in litter boxes, gardens, or in sand boxes in which outdoor cats have defecated.Once an intermediate host ingests sporulated oocysts, the infection results in the formation of tissue cysts in various tissues of the body. Tissue cysts remain in the intermediate host for life and are infectious to cats, people, and other intermediate hosts that eat the cyst-containing tissue. In some cases, T. gondii tachyzoites may be excreted in the milk of infected cows and goats.
 
Keep an eye on these signs and symptoms
Most cats infected with T. gondii show no signs of disease. Occasionally, however, a clinical disease called toxoplasmosis occurs, often when the cat’s immune response cannot stop the spread of tachyzoite forms. The disease is more likely to occur in cats with suppressed immune systems, including young kittens and cats with feline leukemia virus (FeLV) or feline immunodeficiency virus (FIV).
 
The most common symptoms of toxoplasmosis include fever, loss of appetite, and lethargy. Other symptoms may occur depending upon whether the infection is acute or chronic, and the location of the parasite in the body. In the lungs, T. gondii infection can lead to pneumonia, which will cause difficulty breathing that gradually worsens.
 
Infections affecting the liver may cause a yellowish tinge appearance on the skin and mucous membranes. Toxoplasmosis can also affect the eyes and central nervous system (CNS), producing inflammation of the uvea or pigmented part of the eye, the retina, or the space between the lens and cornea (the anterior chamber) abnormal pupil size and responsiveness to light, blindness, lack of coordination, heightened sensitivity to touch, personality changes, circling, head pressing, ear twitching, difficulty in chewing and swallowing food, seizures, and loss of control over urination and defecation.
 
Diagnosis done at the right time to eliminate the dangers
Toxoplasmosis is usually diagnosed based on a cat’s history, signs of illness, and laboratory test results. A definitive diagnosis requires microscopic examination of tissue samples for distinctive changes to the tissues and the presence of tachyzoite. Consult your veterinarian for confirmative diagnosis and proper treatment.
 
Trust your vet for the best treatment
The treatment depends upon the severity of the infection and involves a course of an antibiotic either alone or in combination with other drugs. Treatment should ideally be started immediately after diagnosis and continued for several days after signs have disappeared. If you notice any of the above mentioned
signs or symptoms, get immediate veterinary care.
 
Prevention is always better than cure
Reducing the incidence of toxoplasmosis in cats requires measures to reduce both exposure to infective oocysts and shedding of oocysts into the environment. Cats should preferably be fed commercially prepared, cooked foods (appropriate heating inactivates any T. gondii cysts that may be present) and should not be allowed to eat uncooked meat or intermediate hosts, such as rodents. They should also be denied access to facilities housing food-producing livestock and food storage areas.
 
Parenting a cat does not mean you will be infected with Toxoplasma as it takes a minimum of 24 hours for T. gondii oocysts in cat feces to sporulate and become infective. Frequent removal of feces from the litter box while wearing gloves and washing hands afterward, minimises the possibility of infection. It is unlikely that you would be exposed to the parasite by touching an infected cat, because they usually do not carry the parasite on their fur. It is also unlikely that you would become infected through cat bites or scratches. Indoor cats that do not hunt prey or consume raw meat are unlikely to be infected. The possibility of infection after gardening in soil that has been contaminated with cat feces also exists, and this possibility can be mitigated by wearing gloves and by washing hands after gardening.
 
Take precautions & minimise the risk

• Do not feed unpasteurised milk or raw or undercooked meat to cats.
•  Keep sandboxes covered and cats should not be allowed to use them as litter boxes.
•  Do not allow cats to hunt or roam unsupervised
•  Remove feces from the litter box daily and wash it frequently with boiling water
•  Do not allow pregnant women or immunosuppressed people to clean the litter box
•  As much as possible control populations of rodents

(Dr A Sangaran and Dr ST Bino Sundar are from Department of Veterinary Parasitology, Madras Veterinary College, Chennai, Tamil Nadu)