Understanding Feline Coccidia, Trichomonas, and Giardia

Parasitic Coccidia in Cats and Dogs

Common coccidia affecting both cats and dogs are typically from the genus Isospora. These parasites are usually transmitted through the ingestion of oocysts or sporozoites, which can be found in contaminated environments (for more information, readers may refer to veterinary parasitology texts). The most common symptom of coccidiosis is chronic diarrhea, characterized by weeks of persistent, watery stools. Unfortunately, treatment often has little effect.

Diagnosis involves identifying oocysts in feces, reviewing the animal's medical history, and examining clinical symptoms. Severe, sometimes fatal, coccidiosis can occur before oocysts are detectable, so the presence of oocysts in feces does not necessarily confirm the disease. However, if young cats, dogs, or children exhibit regular diarrhea, coccidiosis should be considered as a potential cause.

Coccidiosis is generally selflimiting and improves as the host's immunity develops. However, oocysts are still shed in the feces. Treating and preventing coccidiosis can be challenging, as conventional deworming medications are ineffective against coccidia, and there are no reliable disinfectants to kill the infectious agents in the environment. Advanced coccidiosis often requires supportive therapy, as no drugs are effective against the coccidia infecting the host. Sulfonamide drugs are commonly used to control the number of coccidia, and in some cases, veterinarians may also use triazine drugs.

Other coccidia that can infect dogs and cats include Cryptosporidium, Toxoplasma, Hammonia, Hepatozoon, Besnoitia, and Plasmodium.

Cat Trichomoniasis

The Trichomonas vaginalis, known as the cause of cat trichomoniasis, is a significant worldwide cause of feline diarrhea. This parasite primarily resides in the vagina, uterus, vulva, prepuce, penis, epididymis, and vas deferens. Trichomonas vaginalis has 35 long flagella and a distinct undulating membrane, making it challenging to identify morphologically.

Cat trichomoniasis can be associated with chronic or recurrent colitis, characterized by increased mucus, foulsmelling, semiformed stools, and the presence of mucus and blood. Constipation, occasional hematochezia, and increased defecation frequency may also occur. The median duration of diarrhea is 135 days, ranging from 1 day to 7.9 years. The anus may become red, swollen, and painful, and fecal incontinence is not uncommon. Most cats remain alert, active, and healthy with normal appetites. Trichomonas can be isolated from the feces of cats without symptoms, with many not experiencing diarrhea. Infected cats are generally young, but infection can occur from 3 months to 13 years of age (median of 9 months).

Diagnosis is made through PCR (polymerase chain reaction), and treatment involves Ronidazole, the drug of choice for treating cat trichomoniasis. It is crucial to accurately calculate the dosage of Ronidazole based on each cat's weight, as an overdose can increase the risk of neurotoxicity. Neurotoxic symptoms include drowsiness, anorexia, ataxia, and seizures. These symptoms usually resolve after stopping the medication but can persist for 1 to 2 weeks. If neurotoxic signs are detected, Ronidazole must be discontinued immediately.

Trichomonas vaginalis is environmentally fragile as it cannot form cysts. It can be killed by drying, refrigeration, exposure to temperatures above 40.6°C (105°F), and longterm exposure to oxygen. During treatment, it is important to change the litter and disinfect the litter box to prevent reinfection.

Cat Giardiasis

Giardia lamblia infections primarily originate from water contaminated with human or animal feces. There are seven species of Giardia, with A and B strains primarily infecting humans, C and D strains primarily infecting dogs, E strains primarily infecting hoofed animals (such as cattle, sheep, pigs, and horses), F strains primarily infecting cats, and G strains primarily infecting rodents. For cats, infections can also occur from D, A, and C strains, and it's important to note that cats can be infected with Giardia A strain, indicating a zoonotic risk, although transmission from cats to humans is relatively rare.

Adult cats with Giardia lamblia infections often exhibit subclinical symptoms, such as temporarily softened stools in the early stages of infection. However, kittens infected with Giardia lamblia may suffer from acute diarrhea, with pale, foulsmelling stools containing mucus.

Diagnosis is primarily through ELISA (enzymelinked immunosorbent assay) or the zinc sulfate fecal floatation test. It is crucial to differentiate Giardia lamblia from Trichomonas vaginalis, as Giardia has a concave ventral disc, a double nucleus, and movement resembling leaf fluttering. In contrast, Trichomonas vaginalis is spindleshaped, unicellular, with a wavy membrane that runs through the entire body, moving in a more irregular and rapid manner.

Treatment includes metronidazole, albendazole, and fenbendazole. In addition to medication, controlling Giardia infections and minimizing the risk of reinfection in treated animals involves the following methods:

1. Environmental净化: Clean the environment to improve treatment effectiveness and eliminate Giardia cysts from the cat's living environment. Remove contaminated feces as frequently as possible, rinse the litter box with water, cover it with disinfectant, and then rinse clean and dry it.

2. Bathing: This can help remove cysts from the cat's fur.

3. Prevent reinfection: Keep drinking water clean and avoid contact with contaminated water sources.

Attention:

If a cat experiences persistent diarrhea, it is essential to identify the potential causes and rule them out one by one. First, exclude any underlying diseases, such as various inflammations. If coccidia, Giardia, and Trichomonas vaginalis are detected, treat accordingly.