Spontaneous cure after natural infection with Gnathostoma turgidum (Nematoda) in Virginia opossums (Didelphis virginiana).

Seasonality of the nematode Gnathostoma turgidum in Virginia opossums (Didelphis virginiana) in the wild has been reported; however, the mechanisms involved in deworming are unknown. We monitored the parasitologic and biologic changes in four Virginia opossums naturally infected with G. turgidum by coproparasitologic examination and abdominal ultrasonography. Eggs became detectable in the feces of opossums in May, peaked in July and August, and suddenly decreased in October. Adults of G. turgidum were expelled in the feces mainly in September. Ultrasonography of the liver showed slight damage during May. Lesions in the stomach appeared in April and persisted until September. The abnormalities of the liver and stomach were resolved in November. These data suggest that G. turgidum is likely expelled as a result of host immunologic mechanisms, although termination of a natural life span cannot be definitively excluded.

Identification of immunodominant peptides from Gnathostoma binucleatum.

Gnathostomiasis is now recognized as a zoonosis with a worldwide distribution. In the Americas, it is caused by the third-stage larvae of Gnathostoma binucleatum and in Asia mainly by G. spinigerum. The availability and preparation of specific antigens are among the main obstacles for developing reliable immunodiagnostic tests. In this study, six immunodominant peptides were identified and characterized from G. binucleatum, somatic antigens (AgS: 24, 32, and 40 kDa) and excretory-secretory antigens (AgES: 42, 44, and 56 kDa) by two-dimensional immunoblot analysis. Among those immunodominant peptides, two AgS spots were characterized by mass spectrometric analysis (32 kDa; pI 6.3 and 6.5) and identified as type 1 galectins. In accordance with this finding, a fraction of AgS exhibited affinity to lactose and displayed a 100% specificity and sensitivity for the diagnosis of human gnathostomiasis.

Is Gnathostoma turgidum an annual parasite of opossums? Drastic seasonal changes of infection in Didelphis virginiana in Mexico.

Gnathostoma turgidum is a nematode that parasitizes the stomach of opossums, Didelphis virginiana. Despite its wide distribution in the Americas, its natural life cycle is poorly understood. Recently, we found an endemic area for G. turgidum infection in Sinaloa, Mexico (Diaz-Camacho et al., 2009). Based on sporadic surveys for several years, the prevalence was apparently high in summer and extremely low in winter. To confirm that this is really a seasonal variance, we conducted a longitudinal survey on G. turgidum infection in opossums from November 2007 to November 2008. The results showed amazing seasonal changes in the prevalence, with synchronized migration and maturation of worms in opossums. Between February and March, many juvenile worms, with occasional AL3, were found in the liver, but no worms were found in the stomach. Mature adult worms began to appear in the stomach around April and rapidly increased in number toward July, when all worms resided in the stomach. Then, the worms disappeared almost completely by November. These results suggest that G. turgidum is an annual parasite of the opossum, D. virginiana, in Mexico.

Identification of estuarine fish Dormitator latifrons as an intermediate host and Eleotris picta as a paratenic host for Gnathostoma binucleatum in Sinaloa, Mexico.

Gnathostomosis is a typical fish-borne zoonotic parasitosis and is currently a serious public health issue in Mexico. Among several Gnathostoma species present in wild animals in Mexico, Gnathostoma binucleatum is the only proven species responsible for human diseases, and the advanced third stage larvae (AL3) of G. binucleatum have been found in over 20 species of fish in this country. In Sinaloa State, two fish species, Dormitator latifrons and Eleotris picta, were heavily contaminated with G. binucleatum AL3. When we analyzed the relationship between the size of the fish and the density of infection with G. binucleatum AL3, the distribution patterns of AL3 were markedly different between these two fish species. Apparent size-dependent accumulation was observed in E. picta but not in D. latifrons, suggesting that E. picta is a paratenic host whereas D. latifrons is a second intermediate host.

Acute outbreak of gnathostomiasis in a fishing community in Sinaloa, Mexico.

An increasing number of human cases of gnathostomiasis have been reported in Sinaloa, Mexico, most of whom have a custom of eating of raw fish dishes such as 'cebiche'. Here we report five adult patients, three women and two men, having an acute episode of vomiting and abdominal pain a few minutes after eating a dish of cebiche prepared from a spotted sleeper perch (Eleotris picta) fished from a nearby lake in southern Sinaloa. All five patients experienced acute throat pain, chest and joint pains, headache and fever. One patient, a 55-year-old male, was hospitalized with suspected pancreatitis and pneumonia. By 8-9 days later, all five patients developed between three and 12 edematous, migrating skin lesions on the back, abdomen, upper and lower extremities, face, eye and scalp. By ELISA, all of them were sero-positive to Gnathostoma doloresi antigen and had elevated IgE levels. Eosinophilia was found in two patients. These patients lived in an agricultural and fishing community. In this community we carried out a sero-epidemiological survey and study of living conditions in a random sample of 309 individuals distributed in 74 households. Frequent consumption of raw fish was reported in 36% of households, and 12 individuals had a clinical history of migrating skin lesions. The sero-prevalence to Gnathostoma antigens was 34.95%. Five fish species and four species of ichthyophagous birds collected from three lakes in the village and a nearby estuary were infected with the advanced third-stage larvae of G. binucleatum, a species found in Ecuador and Mexico. The results describe the first known outbreak of acute gnathostomiasis on the American continent.