GENERAL CHARACTERISTICS
Parastrongylus cantonensis, previously known as Angiostrongylus sp., is a filiarial worm commonly referred to as the rat lungworm.
EPIDEMIOLOGY
The parasite has a worldwide distribution; however, it remains an endemic health threat in Southeast Asia and the Asian Pacific Islands. A variety of rodents serve as the definitive host. The adult worms reside in the pulmonary artery and right side of the heart. Eggs shed by the female lodge in the pulmonary capillaries, where the larvae hatch and migrate up the trachea. The larvae are swallowed and passed in the rodent feces. Once released the larvae infect the intermediate host, mollusks. The mollusks are consumed by a variety of paratenic hosts such as shrimp, fish, crabs, or frogs. The rodents then consume the paratenic hosts and the larvae penetrate the intestine, enter the circulation, and migrate to the central nervous system. Following two successive molts, the larvae then reenter the circulation and migrate to the pulmonary artery. Humans are infected by ingestion of either the intermediate or the paratenic host.
PATHOGENESIS AND SPECTRUM OF DISEASE
The pathogenesis correlates with the worm burden and the site of infection. The larvae may migrate to the central nervous system, causing meningitis or meningoencephalitis. Symptoms include headache, fever, eosinophilia, increased cerebrospinal fluid (CSF) protein, and neurologic manifestations. Occasionally, the larvae may migrate to the eye, causing blindness. Most often the disease is self-limiting.
LABORATORY DIAGNOSIS Definitive
diagnosis relies on histologic identification of the adult female worm. The adult female worm has a distinctive morphologic appearance with spiral, winding, “barber pole” appearing uterus. Highly specific serologic assays are available.
THERAPY
Anthelmintic therapy may be helpful, such as mebendazole. It is important to closely monitor therapy, because the therapy may actually exacerbate the inflammatory response of the host and cause more systemic damage. If larvae are located within the eye, surgical removal is recommended.
