Flagellate protozoa trophozoites of the genus Giardia inhabit the mucosal surfaces of the small intestine, where they attach to the brush border, absorb nutrients, and multiply by binary fission. They usually live in the proximal portion of the small intestine. Trophozoites encyst in the small or large intestine, and the newly formed cysts pass in the feces. There are no intracellular stages. The prepatent period is generally 3—10 days. Cyst shedding may be continual over several days and weeks but is often intermittent, especially in the chronic phase of infection.
The cyst is the infective stage and can survive for several weeks in the environment, whereas trophozoites cannot. Transmission occurs by the fecal-oral route, either by direct contact with an infected host or through a contaminated environment. Characteristics that facilitate infection include the high excretion of cysts by infected animals and the low dose needed for infection. Giardia cysts are infectious immediately after excretion and are very resistant, resulting in a gradual increase in environmental infection pressure.
High humidity facilitates survival of cysts in the environment, and overcrowding favors transmission. Giardia infections cause an increase in epithelial permeability, increased numbers of intraepithelial lymphocytes, and activation of T lymphocytes.
Trophozoite toxins and T-cell activation initiate a diffuse shortening of brush border microvilli and decreased activity of the small-intestinal brush border enzymes, especially lipase, some proteases, and dissacharidases. The diffuse microvillus shortening leads to a decrease in overall absorptive area in the small intestine and an impaired intake of water, electrolytes, and nutrients.
The combined effect of this decreased resorption and the brush border enzyme deficiencies results in malabsorptive diarrhea and lower weight gain. The reduced activity of lipase and the increased production of mucin by goblet cells may explain the steatorrhea and mucous diarrhea that has been described in Giardia -infected hosts.
Giardia infections in dogs and cats may be inapparent or may produce weight loss and chronic diarrhea or steatorrhea, which can be continual or intermittent, particularly in puppies and kittens.
Feces usually are soft, poorly formed, pale, malodorous, contain mucus, and appear fatty. Watery diarrhea is unusual in uncomplicated cases, and blood is usually not present in feces. Occasionally, vomiting occurs. Giardiasis must be differentiated from other causes of nutrient malassimilation eg, exocrine pancreatic insufficiency [see Exocrine Pancreatic Insufficiencyin Dogs and Cats Exocrine Pancreatic Insufficiencyin Dogs and Cats Exocrine pancreatic insufficiency is caused by decreased production of digestive enzymes by the pancreas.
The most common clinical signs are polyphagia, weight loss, and a large volume of loose Diarrhea and weight loss despite an increased appetite are the hallmarks Clinical laboratory findings usually are normal.
In calves, and to a lesser extent in other production animals, giardiasis can result in diarrhea that does not respond to antibiotic or coccidiostatic treatment. The excretion of pasty to fluid feces with a mucoid appearance may indicate giardiasis, especially when the diarrhea occurs in young animals 1—6 mo old.
Experimental infection of goat kids, lambs, and calves resulted in a decreased feed efficiency and subsequently a decreased weight gain. Luckily, there are many things dog owners can do to prevent their dogs from becoming infected with this unpleasant parasite. Here are the facts about Giardia in dogs you need to know to keep your dogs safe.
Giardia is a single-celled parasite that inhabits the intestines of mammals, birds, and amphibians. Each assemblage targets a specific group of animals, but all Giardia assemblages have the same life cycle and mode of transmission.
The lifecycle of Giardia is composed of two stages. The mature parasites , or trophozoites, live in the small intestine where they multiply and eventually become cysts.
Cysts are the infective stage and are shed into the feces of the infected animal. They can survive for several weeks in the environment as cysts, and when they are ingested by an unsuspecting host, they turn into trophozoites and repeat the life cycle. Giardia has to be ingested by your dog in order for him to get the parasite.
Your dog can get Giardia by drinking water that has been contaminated by feces or by eating something that has been contaminated by feces, like grass.
Since dogs love to put things in their mouths, this means that there are plenty of ways your dog can pick up the parasite in his environment, whether it is by chewing on a stick, eating poop , or drinking from a puddle. This is worrisome, especially if you have more than one pet in your household. While transmission from dogs to cats and cats to dogs is unlikely, the transmission from dog to dog is certainly a cause for concern.
If one of your pets is diagnosed with Giardia, talk to your vet about the precautions you need to take to protect your other pets. Giardia in dogs does not always cause problems, but when it does it is highly unpleasant. Giardiasis is the term for the disease caused by the infection, and, as in humans, the most common symptom is diarrhea. The diarrhea can be intermittent or continual, especially in puppies , and failure to diagnose and treat the disease can lead to severe weight loss and even death in extreme cases.
The disease is particularly dangerous for puppies, senior dogs , and dogs with compromised immune systems. The best way to determine whether your dog has Giardia or another condition is to call your vet. However, there are several symptoms of Giardia in dogs that dog owners should be aware of. We agree. Persistent diarrhea is the most common sign of giardiasis, but if left untreated for a long time, weight loss and even death can occur.
In dogs, Giardia is often treated with fenbendazole a dewormer , metronidazole an antibiotic , or a combination of both. And sometimes, a combination of multiple medications including febantel, pyrantel pamoate, and praziquantel can also be effective in treating the parasite in dogs. Follow-up testing at your vet may be necessary if clinical signs continue after treatment is complete.
However, geriatric dogs and dogs with health issues in addition to giardiasis are more at risk for serious problems, including death. They can help you determine if your dog needs to be seen in the clinic.
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