Jamaica Veterinary Medical Association

When one thinks of rats and the zoonotic diseases they potentially carry, in Jamaica thoughts of leptospirosis immediately spring to mind. However, in a presentation given at the recent University of Technology Scientific Conference, Marco-Dean Brown, graduate student in the Department of Life Sciences, University of the West Indies-Mona, indicated that there is another disease concern -  eosinophilic meningitis caused by the rat lungworm Angiostrongylus cantonensis.

According to the presentation, research has shown that rats in all 14 parishes of Jamaica carry the nematode parasite with overall prevalence being 22% (Lindo et al, 2002) to 32% (Waugh et al, 2005). There have been about 24 reported cases or eosinophilic meningitis in humans in Jamaica. A. cantonesis is also known to cause the condition in dogs, though not yet diagnosed here.

While the rat is the definitive host of A. cantonensis, its life cycle also involves a number of intermediate and paratenic (incidental) hosts which could increase the risk to humans and dogs. Mature worms in the rat’s lungs produce eggs which hatch into first stage larvae which migrate up the airways to be swallowed and later passed in the faeces. These develop into infective third stage larvae which are picked up by intermediate hosts, which are snails and slugs, or paratenic hosts, which are lizards, land crabs, freshwater shrimp or planarian flatworms. 

Snails and slugs may contaminate vegetables with the infective larvae which are then consumed by humans. The larvae then migrate to the central nervous system and disease results.

After a very variable incubation period of 1 – 3 weeks or more, symptoms very similar to those of bacterial meningitis occur including headaches, stiffness of the neck, nausea, vomiting, abnormal sensations in the limbs . On occasion there may be ocular manifestations. Cerebrospinal fluid cytology reveals high numbers of eosinophils – characteristic of a parasitic condition. Recovery takes 2 – 8 weeks, but in rare cases serious permanent neurological damage or even death can occur, especially in children. There is no specific treatment as anthelminthic therapy could potentially exacerbate the condition due to a systemic response to the dying worms. Treatment is supportive and is corticosteroid-based.

Further research is to be carried out into the prevalence in potential intermediate hosts in Jamaica, using molecular techniques to improve detection.

Angiostrongylosis is another good reason for careful rodent control, as well as snail and slug control for vegetable crops. Freshwater shrimp or land crabs should be properly cooked and raw vegetables thoroughly washed prior to consumption.  

For more detailed information on Angiostrongylus cantonensis, please click HERE.

References:

Brown, Marco-Dean, Molecular epidemiology of Angiostrongylus cantonensis in Jamaica, University of Technology Scientific Conference, July 2016

http://www.cdc.gov/parasites/angiostrongylus/

Writer's Credit: Unless otherwise stated, all articles on this page are written by Dr. Paul Cadogan.