giardia lamblia
Giardia lamblia (Giardia Duodenalis, Giardia Intestinalis) is a unicellular intestinal parasite responsible for the disease giardiasis.
The life cycle of Giardia
The life cycle of Giardia is quite simple and includes two developmental stages: the cyst stage (the survival form outside the host) and the vegetative stage or trophozoite stage, which is the stage within the host.
The cysts are ingested by the new host through the mouth. Via the stomach, the cysts end up in the small intestine where it bursts open with the result that the trophozoite is released. The parasite can multiply on the spot through dichotomy, but it can also transform into cysts, which are excreted in the faeces.
The trophozoite can only occur in an environment that is favorable for the parasite (the intestines). Outside the body, trophozoites have a short lifespan.
The infectious stage of Giardia is the cyst. Giardia Lamblia cysts enter the body via the faeco-oral route. The acidic environment and other factors in the stomach initiate the excystic process, excysting the cysts and releasing two trophozoites. This process usually takes place in the duodenum (small intestine).
The resulting trophozoites then migrate further into the duodenum and jejunum. The trophozoite is the vegetative form and reproduces asexually in the duodenum by dichotomy. In the duodenum, the trophozoites attach to the intestinal mucosa with their suction cups and cause symptoms such as diarrhea and malabsorption.
Under the influence of bile salts, part of the trophozoites can differentiate again into cysts. Due to this encystification process, the organism loses its mobility and the newly formed cysts are excreted with the faeces. Trophozoites can also be excreted with the faeces by the peristaltic movements of the intestine. Outside the body, the cysts become a potential source of infection for a new host and the cycle is closed.
The incubation period of Giardia Lamblia is between 12 and 20 days. In many animals, infestation will have no clinical consequences, which is then referred to as asymptomatic carrier status. When one shows symptoms, usually in jaundiced animals, which are caused by an infection with Giardia Lamblia, one speaks of giardiasis.
Symptoms
The symptoms are generally characteristic malabsorption problems such as diarrhoea, accompanied by abdominal discomfort, nausea, general malaise, gas formation and greasy foul-smelling stools. This often results in weight loss and weakness.
Diagnostics
An infection with Giardia Lamblia is usually diagnosed in the clinic by microscopy or enzyme linked immunosorbent assay (ELISA).
The sensitivity of microscopy when examining a single sample is relatively low (50-70%), mainly due to the intermittent expulsion of cysts. The sensitivity can be increased by taking, concentrating and fixing samples at several times. When samples are fixed, both trophozoites and cysts can be detected.
ELISA is more sensitive than microscopy (+/- 98% in single assessment), but optimum results are achieved when these techniques are combined. Two fixed faecal samples, taken on different days, are examined microscopically and one sample is tested using ELISA.
Image of Giardia Lamblia (electron microscopy)
Treatment and prevention
When Giardia has been shown to be present, the best advice is to treat all animals.
Metronidazole and fenbendazole are effective against the parasite.
Metronidazole (Flagyl®) is known to sometimes cause neurological side effects at high doses or with prolonged treatment and it is advised not to give it to pregnant or lactating animals.
To combat giardia a treatment of 10 days is necessary.
Fenbenzazole (Veprafen, parazan) is a dewormer for dogs and cats that has also been shown to be effective against Giardia. Treatment should be for 5 days at the recommended dose. Giving other antibiotics is rarely necessary. In addition, there is a risk that the normal bacterial flora in the intestine will die, which in turn will result in permanent diarrhoea.
When the physical condition of the animal is still good, an easily digestible diet can be given in small amounts spread over the day. The easiest way to do this is to use a balanced hypo-allergenic diet food (available from the vet) that contains little fat and lactose and has the right amount of dietary fibre.
In addition to treating the animals, it is advisable to frequently clean and disinfect the environment, food bowls, loungers, brushes and litter boxes. New animals or cats
