Hexametra boddaertii

Nematodes (roundworms) are common parasites which are found in all kinds of animals. The study featured today is a report on a species of nematode reported for the first time in the false coral snake (Oxyrhopus guibei). The false coral snake is a non-venomous snake which mimics the highly venomous coral snakes. The snake in question had been living in captivity for a week at the National Institute of Tropical Medicine (INMeT) in Argentina before it suddenly died. It had appeared healthy until it just keeled over one day. When researchers dissected it, they found that it was full of parasitic roundworms that were identified as belonging to the species Hexametra boddaertii.

(A) The false coral snake a few days after arriving in captivity, (B) Hexametra boddaertii in the snake's body cavity,
(C) Parasitic roundworms in the bowel lumen of the snake, (D) roundworms extracted from the snake's intestine
Photos above from Fig 1 of the paper

The researchers found a total of 120 H. boddaertii in the snake; 68 of which were dwelling in the body cavity while a further 52 were living in the snake's digestive tract. This species of parasite has been recorded in other snakes before, but this is the first time it has been found in the false coral snake, and the first time that it has been reported from Argentina.

Hexametra boddaertii belongs to a group of parasitic roundworm call Ascarididae which also include roundworms that infect various domestic animals and humans. During the snake's stay in captivity, its carers had attempted to deworm it by giving it Fenbendazole - a de-worming drug which is commonly for treating parasitic infections in various domestic animals. They also tried to disinfect the enclosure, but neither seemed to have had any effects on the snake's parasite burden.

When the researchers performed a postmortem examination of the snake, they noticed that the worms found in the snake's body cavity were significantly smaller those found in the gut. On average, the worms dwelling in the body cavity were about 4 cm in length, while those from the gut were about twice as long. It is most likely that those smaller worms were juveniles - one of the key characteristics of ascaridid parasites (including Ascaris lumbricoides which infects humans) are their habit of travelling through the host's body cavity during their juvenile phase (think of it as their coming-of-age, "find yourself" trip) before entering the intestine to settle down and develop into an adult to start reproducing. And those 52 fully-mature worms in the gut had certainly been pretty busy as the snake's faeces were loaded with nematode eggs

But whether they were adults or juveniles, those parasites' presence certainly took their toll on the snake. Parts of the the snake's body cavity showed signs of calcification, its lungs were filled with excess fluid, and its gut lining were inflamed and congested. Given the number of worms the snake had and how well-developed most of them were, the snake most likely had acquired those parasites long before it was brought into captivity.

In addition to providing a new parasite record, this study also revealed a potential risk associated with handling snakes - larvae of other Hexametra nematodes from snake faeces have been reported to successfully infect the crab-eating macaque, so if given the opportunity, there is some potential for H. boddaetii to jump host into primates (including humans).

Sometimes when it comes handling snakes, it is not necessarily just the snake that you have to be careful of...

Peichoto, M. E. et al. (2016). First report of parasitism by Hexametra boddaertii (Nematoda: Ascaridae) in Oxyrhopus guibei (Serpentes: Colubridae). Veterinary Parasitology 224: 60-64.