Macracanthorhynchus hirudinaceus in a Sow in El Oro Province - Ecuador

Abstract

Background: Macracantorhincosis is a zoonotic disease resulting from inadequate sanitary conditions, which occurs in pigs infected by acanthocephalic helminths called Macracanthorhynchus hirudinaceus. The eggs of these parasites are resistant to cold, high temperatures and can survive up to three years in the soil. They are consumed by dung beetles of the Scarabeidae family causing the parasite to evolve into its infective form, the cystacanth. The pig becomes infected after ingestion of either larvae or adult forms of these coleoptera. This paper describes a case report of macracantorhincosis found in a pig from the canton of Zaruma located in the province of El Oro, Ecuador.

Case: A female pig, approximately 24 months old, weighing 30 kg, presented cachexia, muscle weakness, pale oral and ocular mucosa and a body temperature (rectal) above 39.4°C. The animal had a bulge on the ventral side of the neck, which evolved causing progressive discomfort to the point that the animal stopped eating. The pig was dewormed for three consecutive days. Fifteen days later, the animal had convulsions and muscle tremors, and died some hours after the symptoms started. During necropsy procedure, pale digestive tract membranes and nodules with fibrin were observed in the small intestine (jejunum), which was incised and the presence of parasites adhered to the granulomas detected. Two granulomas for morphological and histological studies and stool samples for coproparasitic test were collected. The collected parasites were fixed in a 10% buffered formalin solution, cross-sections were made and routinely processed for histological studies. The 5-μm-thick sections were stained using the hematoxylin and eosin (HE) technique. The parasite’s action involves perforation of the intestinal wall though its proboscis causing peritonitis and enteritis. Other conditions in intestinal dissection such as necrotic areas, inflammation of the submucosa and adult parasites adhered to the intestinal mucosa were also observed. The coproparasitic examination was performed using the flotation and sedimentation techniques. The coproparasitic test detected dark colored feces, semi-solid consistency and the presence of Macracanthorhynchus hirudinaceu eggs. In the histological evaluation of the cross section of the parasite, the presence of circular and longitudinal muscle fibers and lemniscus with their constrictor muscles was observed. Cuticle, hypodermis with tapered fibers and a large number of developing mature eggs were also reported.  

Discussion: There is no pathognomonic symptomatology about this parasitosis, peritonitis can be generated by intestinal perforations. The findings at necropsy were ulcerations, inflammation in the small intestine and the presence of numerous nodules in the serous layer, where there was penetration of the parasite's proboscis. When fixed to the mucosa, these parasites cause ulcerations, inflammation and necrosis in the wall of the small intestine. The hypodermic layer is thicker than the muscular layer and the presence of leminis with their constricting muscles are typical features of acanthocephalus. It is considered appropriate to carry out epidemiological studies on the prevalence of the parasite Macracanthorhynchus hirudinaceus at pig farming system in the region, in order to determine the main risk factors. In Ecuador, cases of this disease in humans have not yet been reported, but have already been described in other countries, so the presence of this parasite in family swine farming may be considered a zoonotic-type risk factor.

Keywords: pig, zoonotic disease, macrocanthorhincosis. 

Título: Macracanthorhynchus hirudinaceus em uma porca da Província de El Oro - Equador.

Descritores: suíno, doença zoonótica, macracantorrincose.