Giardia in Cats
By Dawn Skupin
Gastrointestinal parasitism is a common problem in cats, with rates of incidence as high as 45 percent. Giardia are single celled parasitic organisms, (protozoa), found in the intestines of its host. These microscopic organisms attach to the intestinal wall or swim freely in the mucous lining of the intestine.
In the past, Giardia was given a different name whenever it was discovered in a new host so that a variety of names were attached to Giardia, e.g. G. canis in dogs and G. cati in cats. Today, scientists believe that only a few species occur, each capable of infecting more than one host, cat, dog, cattle, etc. It is generally believed that animals younger than three years of age are more often infected than older cats, with kittens being the most susceptible. The host immune/inflammatory response may also be a contributing factor in the pathology of the Giardia infection.
This pesky parasite is seen worldwide in most domestic and wild mammals, many birds and people. Giardia is a waterborne protozoon which is VERY DIFFICULT TO DETECT! Only at certain cycles will the testing for Giardia be conclusive. The best method for detection is to have your veterinarian perform an endoscopy. Second to the endoscopy method requires multiple fecal testing over several days because of the intermittent nature of Giardia. Samples provided by bringing a stool sample to your vet may not be accurate. This method may bring a false report for the parasite. Fecal floatation, (zinc sulfate solution), for cysts are not accurate as trophozoites will NOT be detected because the floatation solution lyses the trophozoites. ELISA and IFA testing for Giardia antigens in feces is highly sensitive and specific in humans, but some studies suggest that they are less so when used in domestic animals.
Flagellate protozoa (trophozoites) of the genus, Giardia, inhabit the mucosal surface of the small intestine. There they attach to the brush border, absorb nutrients, and multiply by binary fission. Trophozoites encyst in the small or large intestine and pass in the feces. At this point, the cyst is the infective stage, and transmission occurs by the fecal-oral route. Cats become infected with Giardia by eating food or drinking water contaminated with cysts. Cyst shedding may be continuous over several days and weeks but is often intermittent. Although occasionally passed in the feces, trophozoites are not infective. Incubation periods are generally 5-14 days. Cysts can survive in the environment, but trophozoites cannot. Giardia cysts are resistant to both freezing and chlorination of water and can live for several months if not dried out or exposed to sunlight. High humidity, overcrowding and dirty water/food bowls favor survival of cysts and transmission of the parasite.
Following a one to two week incubation period, both people and cats initially suffer acute gastrointestinal intestinal tract infection resulting in diarrhea. Fever is much less common than with bacterial agents of gastroenteritis. This acute phase of the disease is often followed by a chronic syndrome of malabsorptive diarrhea, weight loss and abdominal pain that is cyclical. The stools are watery at the onset of symptoms, but then typically progress to soft, semi formed stool with a distinctive rancid, foul odor. The diarrhea may continue indefinitely if not treated.
Symptoms of Giardia include but are not limited to:
· Intermittent loose stools, rancid and foul odor
· Lack of appetite
· Nausea or Vomiting
· Some cats will eat but still keep losing weight
· Have excessive gas
· Coats may be dry or brittle
It is important to note that whether or not Giardia in cats can be transmitted to humans is still controversial. Until scientists resolve this question, it is better to assume it is possible. Infected animals and birds can clearly serve as a source for contamination of the environment with the organism and must be considered as a potential zoonotic risk. There is a human form of giardia, but since there are several strains of giardia, it is possible that any given strain might not spread from feline to human. Human giardiasis is also caused by drinking contaminated well water. The organism survives well in cold water and may not be inactivated by routine chlorination tablet water purification systems. Filtration of water is essential.
Not all cats infected with Giardia will become sick. Cats may host the organism for several years, while passing it on to other cats, before showing any clinical signs of Giardia. An immune-suppressant factor, such as FIV, FeLV or overall debilitation, may hasten the onset.
Treatment options for cats include:
· Metronidazole (e.g. Flagyl) can be used in cats, but not pregnant animals
· Albendazole (e.g. Valbazen) was recently found to be quite effective in dogs, and may be more effective than Metronidazole in stopping the shedding of cysts. Not for use in pregnant cats.
· Fenbendazole (e.g. Panacur or Drontal-Plus) Used in cats at 50 mg/kg for 3 to 5 days. Fenbendazole has been shown to be completely effective in eliminating experimental Giardia infections. Safe for use in pregnant queens.
· A whole-organism vaccine, (Giardia Vax, Fort Dodge Animal Health), has been approved for use in dogs. It has been shown by the manufacturer to reduce shedding of Giardia cysts after experimental infection.
Parasite reinfections are very common, but can be prevented. Parasite control begins with good sanitation procedures. This includes daily removal of feces; washing the litter boxes with a disinfectant or bleach; bleach food and water bowls on a regular basis; avoiding overcrowded conditions by limiting the amount of animals in a specific area; avoid diets with raw meats as it could be contaminated; and controlling intermediate hosts, (fleas, ticks, and rodents). Clearly, controlling parasites promotes healthy cats and kittens.
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