Larva Migrans In Humans Research Articles

Gnathostomiasis in wild boars from Japan.

Gnathostoma doloresi, a nematode parasite producing ulcerative and/or granulomatous lesions in the gastric wall of domestic pigs and wild boars (Sus scrofa leucomystax) throughout southeastern Asia, is an important zoonosis causing cutaneous larva migrans in humans. Patients infected with G. doloresi have been found yearly in the vicinity of Miyazaki Prefecture, Japan. Adult nematodes were found in 31 of 32 wild boars captured at two different geographic locations in the prefecture, a location in the high mountains and one at sea level. The parasite-free animal had gastric lesions typical of a previous infection with this parasite. The nematode intensities were higher in wild boars caught in the mountains than those caught at near sea level. The extremely high prevalence of G. doloresi in wild boars indicates that the life cycle of this parasite is well established in this area of Japan.

Gnathostomiasis in frog-eating snakes from Japan.

Gnathostoma doloresi parasitizes the gastric wall of wild (boars) and domestic (pigs) swine (Sus scrofa). Its larvae cause cutaneous larva migrans in humans. Amphibians, reptiles and a freshwater fish are infected with the advanced 3rd stage larvae. Prevalence of G. doloresi larvae were surveyed in several snakes, especially in a common frog-eating snake (Rhabdophis tigrinus). All species of snakes examined were infected with G. doloresi larvae suggesting that snakes are important reservoir hosts. Prevalence of G. doloresi larvae in frog-eating snakes was lower than that found in mammal-eating snakes. Thus, as a source of infection to snakes, small mammals may be more important than frogs in the natural life cycle of G. doloresi in Japan.

Parasites, Pets, and People

It is important for the family physician to understand that patients' relationships with their pets play an important role in helping maintain mental and physical health yet provide the potential for causing illness in the patient. Toxocara canis (dog roundworm) and Toxocara cati (cat roundworm) are the ascarids most commonly responsible for VLM and ocular larva migrans in humans. These roundworms live in their adult stage in the small intestine of the dog and cat where their eggs are passed in the feces. The eggs containing the infective larva are very sticky, thus an infant crawling around on the floor can easily pick these up on fingers that almost invariably end up in the mouth. Infections are usually mild and asymptomatic but with a persistent eosinophilia. Ocular larva migrans is the form usually occurring in older children and adults. Some public health veterinarians recommend that a puppy or kitten should not be obtained as a companion for a child who is not old enough to read, thus bypassing the crawling and toddler stages. Hookworm eggs, shed in the feces of infected dogs or cats, develop into the infective second stage within a week. Humans are usually infected when bare areas of skin such as bare feet or the torso come in contact with soil contaminated with the larvae. The second-stage larvae are able to penetrate the intact skin of humans and the foot pads of dogs and cats. In the United States, the common dog hookworm, A. caninum, is a widespread parasite. Human intestinal ancylostomiasis caused by this species is rare, with only six cases recorded in the literature. Infection in humans or animals by the common tapeworm of dogs and cats (Dipylidium caninum) requires ingestion of the intermediate host, the dog or cat flea containing the larva (cysticercoids) of the agent. Many cases in humans are asymptomatic. Dipylidiasis affects mainly infants and young children who may swallow a flea that hops up while the infant is crawling on the floor or fondling the family pet. Humans appear to be highly resistant to the infection, given the high frequency of flea infestation on dogs and cats and the relative rarity of human disease. Pinworms of animal hosts are not transmissible to humans. Humans become an accidental host of dirofilaria when bitten by an infected mosquito, although the microfilaria will not mature to the adult form in humans. Radio-opaque coin-type lung lesions can be noted on radiographs.(ABSTRACT TRUNCATED AT 400 WORDS)

Visceral Larva Migrans and Alveolar Hydatid Disease: Dangers Real or Imagined

For both visceral larva migrans and alveolar hydatid diseases, it is the feces of companion animals that are the primary source of human infection. Clearly, whatever is done to reduce this form of environmental contamination and the prevalence of the parasites' infective stages will help to protect the health of the human population in the United States and Canada, particularly the children. Very important are appropriate anthelmintic treatment programs, especially for T. canis, and proper control of close associations between pets and people. Probably the known incidence of visceral larva migrans in humans and the range of its known pathogenicity will increase as better diagnostic methods become available. In addition, other animal helminths, for instance Toxocara cati and Toxascaris leonina, may become more substantially documented as causes of human visceral larva migrans. Until more is known of the geographical distribution and prevalence of Echinococcus multilocularis among animals in North America, it will be difficult to assess accurately the future significance of alveolar hydatid disease in the continent's human population. Another important advance would be the development of anthelmintics that are effective for somatic second stage larvae of T. canis, and others effective for adult or larval Echinococcus species. Meanwhile it is a most important responsibility of the veterinary profession to educate its clients thoroughly concerning these dangerous helminths.