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Amoeba (Entamoeba invadens) infection in boas and pythons2015-09-28

Amoebiasis in considered as one of the most severe parasitic infections in both boas and pythons. Our recent article is dedicated to help keepers in recognition of this significant disease at early stages...

Despite, amoebiasis being less known and less hyped for most boa enthusiasts compared to other infectious diseases (f.i. IBD), amoeba infection is one of the most significant diseases, as it can wipe out entire captive snake collections in a very short period of time.


The pathogen

Entamoeba invadens is a protozoa (one-celled parasite) species and a close relative to human pathogen agent Entamoeba histolytica. One must notice that Entamoeba invadens is present in most herbivore and omnivore reptiles (chelonians, skinks, geckos, etc.) without causing any clinical symptoms or illness. However, it can cause severe disease in carnivore reptiles. Entamoeba invadens is not host-specific, it has a wide spectrum of hosts instead. 

The infection enters the host mostly by contaminated water, sometimes by food. Arthropods are considered as mechanical vectors in spread of the disease. This protozoal agent features high morbidity and high mortality: during an outbreak, whole collections can be perished in as short time as only 1-2 weeks.   


Clinical symptoms

Generally, amoeba infections merely has specific symptoms. The most typical symptom- severe, sometimes haemorrhagic diarrhea -may became apparent only at late stages, sometimes just prior to mortality. Regurgitation of undigested food, dehidration, muscle weakness may occur as well. 
By lacking of recognition and starting an adequate treatment in time, the majority of snakes infected could die in a few days. The minority may last for few weeks more, while they will be shedding amoeba cysts by faeces and will become a reasonable source of infection for other snakes.

Autopsy describes a severe inflammation of lower small intestines and colon with mucosal erosion, ulceration, haemoragghia, necrosis in acute cases. In chronic cases, thickening of mucosa and subsequent occlusion of lumen is visible. Necrotic lesions are often found in the liver, rarely in the kidneys, as well.


Diagnosis

This infection can be diagnozed by examining fecal samples. Keepers only have to collect a fresh sample from stool and pass it to an eligible Animal Health Institute. The procedure is relatively quick and cheap.


Prevention and treatment 

As in case of all contagious diseases, prevention must be ephasized. Proper quarrantine system, strict hygiene are essentials. Regular disinfection of water bowels, drinking dishes are important, as amoeba cysts most often spread by contaminated water. Not to neglect the role of arthropod vectors in spreading, though.
Snakes must not be kept by potential amoeba hosts (chelonians, skinks, geckos, etc) together.

Freashly acquired wild-caught snakes must be examined for internal parasites, including Entamoeba as a routine.
Snakes showing clinical signs of amoebiasis should be treated immediately, treatment should not wait for parasitic findings, as snakes can die without adequate treatment in the meantime.

Several different antibiotics have been used for treatment in the last few decades, however most authors still recommends metronidazole as a first choice. There are some debates regarding the doseage and repeats,  however. Some sources suggest high dosage used only one singular time, as these authors had noticed neurological signs after repeating metronidazole in low dosage for 3 straight days. Supportive therapy such as fluid replacement, vitamins may also be given.

Most ill snakes will get better relatively quickly, with no side-effects taking place.


References.:


Am J Vet Res. 1975 Jun;36(6):807-17. Epizootic of fatal amebiasis among exhibited snakes: epidemiologic, pathologic, and chemotherapeutic considerations.

http://www.animalhospitals-usa.com/reptiles/snakes/snake-diseases/snake-parasitic-diseases.html

http://www.ratsnakefoundation.org/

Dr. Botond Ádám

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