Abdominal Calcifications in a Patient From the Congo Basin with History of Snake Meat Consumption: Radiographic Evidence of Prior Armillifer Infection

Abstract

We report a case of a 60-year-old asymptomatic male with history of consumption of uncooked snake meat while living in the Congo basin and prior imaging showing multiple abdominal calcifications. Patient had multiple subepithelial colonic lesions identified during screening colonoscopy and microscopic examination of the lesions demonstrated a calcified nodule in the submucosa with overlying normal mucosa. However, no parasite was identified within the calcified nodule. Given the history of consumption of uncooked snake meat and the typical radiographic feature of multiple abdominal calcifications, it is very likely that the patient’s radiographic abnormalities are due to prior Armillifer armillatus infection, a parasitic infection acquired from consumption of uncooked snake meat. Patient was asymptomatic at the time of evaluation and was not given anti-parasitic treatment.

Introduction

Armillifer is an endemic zoonotic infection in tropical countries, and there are rare reports of imported infections among African immigrants. ¹ In this article, we are reporting a case of prior Armillifer infection in a patient who immigrated to the United States from West Africa.

Case Description

A 60-year-old male with pre-diabetes, hypertension, and hyperlipidemia, was referred for evaluation due to finding of scattered calcifications in the liver and peritoneal cavity (Figure 1) in a computed tomography (CT) abdomen and pelvis performed at a different institution 2 years prior for evaluation of nausea and vomiting. At the time of presentation, patient denied fevers, chills, nausea, vomiting, abdominal pain, change in bowel habits, rectal bleeding, melena, or unintentional weight loss. Patient reported consumption of uncooked snake meat on numerous occasions while living in the Congo basin until he immigrated to the United States, 5 years prior to presentation.

Figure 1.

Multiple, scattered calcifications in the liver and peritoneal cavity.

Patient underwent colonoscopy for colon cancer screening and multiple subepithelial lesions measuring 5 to 10 mm in diameter were identified in the cecum, hepatic flexure, transverse colon, and rectum. A few of the larger lesions (Figure 2) were sampled and microscopic examination of these lesions demonstrated a calcified nodule in the submucosa with overlying normal mucosa (Figure 3). Periodic acid Schiff (PAS) stain did not demonstrate a parasite within the calcified nodule.

Figure 2.

Subepithelial colonic lesion (red arrow).

Figure 3.

Calcified nodule (red asterisk) in the submucosa with overlying normal mucosa (red arrow).

Given the patient’s history of consumption of uncooked snake meat while residing in the Congo basin, and radiographic findings of abdominal calcifications, it is very likely the patient had prior parasitic infection with Armillifer, most likely Armillifer armillatus species as it is the most common species in the African countries. Additionally, the subepithelial lesions sampled during the colonoscopy could represent calcified lesions from prior Armillifer infection. Since the parasites degenerate 2 years after infection, pathological examination of the calcified lesions will not demonstrate the parasite. As our patient was asymptomatic, he was not given anti-parasitic treatment. Patient remained symptom free during his 1 year follow-up.

Discussion

Armillifer in a zoonotic parasitic infection and 4 species of pathogenic Armillifer have been recognized: A. armillatus in Africa and Arabian countries, A. grandis in Africa, A. agkistrodontis in China, and A. moniliformis in Southeast Asia.^2,3 Among the 4 species, A. armillatus is most frequently encountered. Annulations are used for identification of the species (A. agkistrodontis: 7-9, A. armillatus 18-22, A. grandis >25, A. moniliformis 30). ⁴

Definitive hosts are snakes, and the adult worm resides in the nasopharynx, trachea, or lungs of the snake.^5,6 Adult worm has a cylindrical body with marked annulations, blunt tail, and mouth with pair of retractile hooks on either side, which allow the parasite to enter the blood vessel and migrate to distant organs. ⁷ The eggs produced by the adult female worms are resistant to gastric juice and are found in respiratory secretions of the snake and in contaminated grass or water.^7,8 The secondary hosts commonly acquire the infection by consumption of snake meat, direct contact with the snake meat or ingestion of eggs from contaminated food or water. ³ The nymphal forms are found in secondary hosts and an important step in the completion of the life cycle of the parasite is ingestion of the animal containing the encysted nymphs by the snake.^8,9

Bushmeat consumption is increasing in the Congo basin due to the scarcity of other protein sources secondary to deforestation in the area. ¹⁰ If snake meat containing the parasite eggs are ingested by the humans (accidental hosts), the life cycle of the parasite comes to an end. ¹⁰ The larvae pass through the intestinal wall and encyst in the liver, spleen, mesentery, or pleura and grow to a length of 16 to 20 mm.^6,8 The incidence of the disease in humans is very likely underestimated as most patients are asymptomatic.^6,10 The commonly involved organs are intestine, liver, spleen, lungs, and lymph nodes and rare cases of ocular involvement have been reported.^8,11 Symptoms depend on the organs involved. Most commonly patients develop chronic cough, or abdominal pain. ² Severe infestations can cause meningitis, pneumonitis, pericarditis, intestinal obstruction, peritonitis, obstructive jaundice, nephritis, prostatitis, and death.^3,9 Dying larvae release antigens provoking an intense immune reaction and can be possible explanations for neurological signs and death.^5,10

The diagnosis is reached based on incidental findings on autopsy or radiographic studies or exploratory laparotomy. ³ Patients may have mild eosinophilia and elevated erythrocyte sedimentation rate (ESR). ² Serology and polymerase chain reaction (PCR) testing for diagnosis have been developed, but not widely available. The calcified nymphs of A. armillatus have a typical appearance with multiple, comma shaped calcifications which corresponds to the convexity of the curved nymph within the cyst.^2,7 Cysticercosis is a parasitic infection which can cause calcifications similar to the Armillifer species. However, these calcifications are restricted to the brain and skeletal tissue, and never seen within the thoracic or abdominal cavities. ² To rule out cysticerci, x-ray of the muscles of the thigh or extremities can be performed. ⁷

Microscopically, 3 types of lesions have been described: (1) minimal or cellular infiltration with viable nymph surrounded by thin fibrous capsule; (2) necrotic granuloma with dead nymph, release of antigens and activation of immune cells; and (3) granulomatous scar with lymphocytes in the absence of the typical structure of the parasite. ¹² In our patient, a calcified nodule was seen in the submucosa without evidence of a parasite.

Treatment is not necessary in asymptomatic patients as the parasites degenerate after 2 years. ² No standard anti-parasitic treatment is available; there are reports of treatment with praziquantel, albendazole, or mebendazole use in these patients.^2,3 In patients treated medically, cure rate is roughly 50%. ¹³ Antibiotics and surgery are indicated in patients with secondary infectious complications. ³ There are cases of symptomatic infection successfully managed by surgery.^3,6 Risk of parasite transmission can be reduced by removing parasites while slaughtering snakes, hand washing after handling snake meat, and adequate cooking of snake meat. ¹⁰