FTÄ Mikrobiologie
Hexamita
DEFINITION/OVERVIEW
Hexamita is a small flagellate parasite which can be found in the intestinal tract of chelonians and snakes. Hexamita parva is the usual cause of disease in chelonians. Disease has not been reported in other reptiles.
ETIOLOGY/PATHOPHYSIOLOGY
Infection is thought to occur by ingestion of an infective cyst, which passes into the gastrointestinal tract.
Reproduction is by simple binary fission. Subsequently, the parasite may ascend via the bile ducts to the gall bladder or via the ureters to the kidneys, where it encysts, resulting in inflammation.
Alternatively, Hexamita may pass through the gastrointestinal tract without resulting in disease.
Transmission can occur via urine or feces.
SIGNALMENT/HISTORY
Disease has been described in a wide variety of chelonian species with no “typical” signalment.
CLINICAL PRESENTATION
Animals with Hexamita infection may be asymptomatic or have non‐specific signs such as lethargy and reduced appetite.
If significant renal pathology is present, weight loss and polydipsia may be seen.
RISK FACTORS
Husbandry
Poor hygiene will increase the risk of disease transmission.
Others
Pre‐existing renal or biliary disease or concurrent parasite infection have been suggested to be potential risk factors.
Identification of the parasite in a sample of urine ± feces may lead to suspicion of disease, but flagellates are not always associated with pathology.
Definitive diagnosis requires detection of the parasite on renal biopsy in a live animal.
DIFFERENTIAL DIAGNOSIS
Parasites should be distinguished from commensal intestinal flagellates, especially trichomonads, which may commonly be seen in fecal samples or urine samples contaminated with feces.
DIAGNOSTICS
Analysis of a fresh urine sample may reveal small fast‐moving flagellates (< 8 microns) characterized by six anterior flagella.
In small samples the parasite will rapidly desiccate and die.
Renal biopsies should be submitted for histopathology.
Biochemistry may be helpful to indicate degree of renal damage.
PATHOLOGICAL FINDINGS
Characteristic postmortem findings include pale enlarged kidneys with dilated collecting tubules. Bile ducts appear thickened with a dilated lumen.
On histopathological examination, flagellates may be visualized within the renal tubules and bile ducts with associated inflammatory changes.
APPROPRIATE HEALTH CARE
Treatment involves both eliminating the parasite and supportive care of the renal disease.
Euthanasia may be considered in severe cases of renal failure.
NUTRITIONAL SUPPORT
Some patients may be anorexic and severely dehydrated on presentation.
Fluid deficits should always be corrected and nutritional support provided as needed.
CLIENT EDUCATION/HUSBANDRY RECOMMENDATIONS
Hygiene measures should be reviewed to minimize the risk of disease transmission.
DRUG(S) OF CHOICE
Metronidazole is the most common choice for treating Hexamita.
Various treatment regimens have been recommended ranging from 100–125 mg/kg PO once, then repeated after 14 days to 50 mg/kg PO q24h for 3–5 days for severe infections.
PRECAUTIONS/INTERACTIONS
Hepatotoxicity and CNS toxicity have occasionally been reported in other species following metronidazole use, so care should be taken if pre‐existing hepatic dysfunction is suspected.
PATIENT MONITORING
Response to therapy is usually monitored by a reduction in clinical signs (e.g., improved appetite).
Repeat blood samples can also be taken to recheck renal parameters.
EXPECTED COURSE AND PROGNOSIS
The prognosis for patients with extensive biliary or renal damage is poor, but if diagnosed early the condition can be managed successfully.
If left untreated, the disease will slowly progress to renal failure and death.
