Pila ampullacea and Pomacea canaliculata, as new paratenic hosts of Gnathostoma spinigerum.

Aquatic snails, Pila ampullacea and Pomacea canaliculata were experimentally found to be suitable paratenic hosts for advanced third-stage larvae (L3) of the nematode Gnathostoma spinigerum, the causative parasite of gnathostomiasis in humans. G. spinigerum (L3) were found to be encapsulated in the tissue of the snail's foot and its internal organs. The infection, intensity and survival of third-stage larvae of G. spinigerum in both species of aquatic snails are described. This is the first evidence to reveal that not only vertebrates but also invertebrates (snails) can serve as paratenic hosts to this parasite. Aquatic snails are one of several sources of human gnathostomiasis in Thailand.

Capillariasis: chronic watery diarrhea--not only from microorganisms.

A 54-year-old male Thai patient from Prachin Buri Province presented with a history of chronic watery diarrhea for many years. He passed stool five to ten times per day with occasionally colicky pain, abdominal distension, nausea and vomiting. He had visited hospitals and private clinics and received treatment but with no improvement. He presented to the Hospital for Tropical Diseases, Bangkok, Thailand, where on physical examination, he had moderate dehydration, weakness, abdominal distension and a gurgling abdomen. The eggs, larvae and adult worms of Capillaria philippinensis were found on stool examination. The patient was admitted and treated with Mebendazole for 20 days, whereupon his symptoms resolved. Two months previously, he had ingested a raw small fresh-water fish dish called "Phra-Pla Siw/Soi". Small fresh-water fish near the patient's home were collected and examined for Capillaria philippinensis larva. The results were negative for parasitic organisms.

Host-finding behavior of Strongyloides stercoralis infective larvae to sodium cation, human serum, and sweat.

The host-finding behavior of Strongyloides stercoralis infective larvae was examined by in vitro agarose assay method. As human body fluid contains 0.85% (ca 0.15 molar) NaCl, various concentrations of sodium chloride, from 0.5M to 0.01M (7 steps), were examined. Many larvae were attracted at concentrations between 0.5 and 0.05M of sodium chloride. The concentration of 0.05M attracted the most larvae. The concentration of 0.02M of sodium chloride showed greatly reduced larval attraction compared with 0.05M. Therefore, the threshold concentration was determined as 0.05M. Then, 0.05M of chemicals were examined in a further experiment. Chloride compounds (NaCl, KCl, CaCl2, MgCl2) were investigated. These chemicals are components of human body fluids. Distilled water was used as the control in all experiments. Only sodium chloride attracted the larvae. Next, alkaline compounds were examined [NaOH, KOH, Ca(OH)2, and Mg(OH)2]. Larvae accumulated only at the NaOH site. The results suggested that the Na cation is important for larval attraction. A high pH value did not influence attraction at all. Next, human serum was tested. The human serum used was from normal serum to 1:32 diluted sera by distilled water (7 steps). Hierarchical attraction was seen according to serum concentration. Next, human sweat was collected from a limited zone of chest skin where only eccrine glands were distributed. Non-diluted sweat attracted the most larvae. Sweat might act as one of the most probable factors for infection by this skin-penetrating nematode.

Gnathostoma infection in fish caught for local consumption in Nakhon Nayok Province, Thailand I. Prevalence and fish species.

Between August 2000 and August 2001, 12,216 fish of 73 species were purchased from several local markets in Nakhon Nayok Province, Thailand, and examined for the presence of Gnathostoma larvae. Almost all species were fresh-water fish that had grown naturally, rather than raised commercially. Eight species were found to be infected with gnathostome larvae. The overall prevalence was 5.1% (626/12,216) and a total of 5,969 larvae was recovered. The highest rate of infection (30.1 %) was found in Monopterus albus (swamp eel). The rates in the remaining infected fish were as follows: Anabas testudineus (climbing perch) 7.7%, Channa striata (striped snake-head fish) 7.4%, Clarius macrocephalus (Gunther's walking catfish) 6.7%, Channa micropeltes (giant snake-head fish) 5.1%, Channa lucius (blotched snake-head fish) 4.0%, Clarius batrachus (Batrachian walking catfish) 1.4%, and Ompok krattensis (butter sheatfish) 0.6%. The mean number of larvae/fish was highest in swamp eels (10.0 larvae/eel), and the maximum number of 698 larvae was recovered from one eel. The body sizes of the recovered G. spinigerum advanced third-stage larvae were 2.70-5.10 mm in length (average, 3.97+/-0.50 mm) and 0.29-0.60 mm in width (average, 0.40+/-0.04 mm). The average number of cephalic hooklets of the larvae from rows 1 to 4 were 41.8+/-0.5 (range, 40-43), 43.6+/-0.6 (range, 42-45), 46.1+/-0.9 (range, 44-48) and 49.3+/-0.7 (range, 48-51), respectively.

Soil-transmitted helminthiases and health behaviors among schoolchildren and community members in a west-central border area of Thailand.

The prevalence of soil-transmitted helminthic infections and health behaviors related to infections in schoolchildren and villagers of a community (4 hamlets) was studied in Hauy Kayeng subdistrict, Thong Pha Phum district, in the north of Kanchanaburi Province. The intestinal helminth infection rate of the schoolchildren was 15.6%. Hookworm infection was the most prominent (9.8%), followed by Trichuris trichiura (6.2%), and Ascaris lumbricoides (2.2%). The community showed higher prevalence rates and was infected with more types of intestinal helminths than the schoolchildren. Thirty-five point two percent (35.2%) of the residents were infected with soil-transmitted helminths, 30.5% with hookworm, 3.4% with A. lumbricoides and 2.2% with T. trichiura. Almost all hookworm cases (94.3%) were light intensity infections, while only 1.3% were heavy infections. Moreover, the hookworm infection rate in the community was found to be much higher when a stool culture method was used (39.1%). With this technique, 2.3% Strongyloides stercoralis infections were detected in the community population. Examination of the health behavior of the study samples showed that approximately 75% always defecated in a toilet. Schoolchildren who always wore shoes comprised 67%, which was lower than the community, at 85%.

Antioxidant enzyme levels in the erythrocytes of riboflavin-deficient and Trichinella spiralis-infected rats.

The erythrocyte antioxidant enzyme levels of catalase, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) of riboflavin-deficient and Trichinella spiralis-infected rats were investigated. The rats were deprived of riboflavin at the 8th week of the experiment. At that time, the erythrocyte glutathione reductase activity coefficient (EGR AC), as an indicator of riboflavin status, was > or = 1.30 in rats fed a riboflavin-deficient diet and T. spiralis-infected rats fed a riboflavin-deficient diet showed no biochemical sign of riboflavin deficiency. At the 12th week of the experiment, the levels of catalase, SOD and GSH-Px were significantly lower in the riboflavin-deficient, T. spiralis-infected, and combined riboflavin-deficient and T. spiralis-infected, rats, compared to the control group. This may have been due to an increase in free oxygen radicals caused by riboflavin deficiency and parasitic infection.

Gnathostoma infection in Nakhon Nayok and Prachin Buri, Central Thailand.

Gnathostoma infection in Nakhon Nayok and Prachin Buri Provinces, Central Thailand, was investigated. The prevalence and intensity of infection of swamp eels were determined; dog fecal samples and fresh-water copepods were examined for evidence of infection. The overall prevalence of eel infection was 38.1% (117/307) in Nakhon Nayok and 24.0% (74/308) in Prachin Buri--the former rate being significantly higher than the latter. Most of the positive Nalkhon Nayok eels (53.8%) harbored only 1-9 larvae; only one eel bore more than 50 larvae. In Prachin Buri, 67.6% of the positive eels harbored 1-9 larvae; again, only one eel bore more than 50 larvae. The mean number of 11.0 +/- 10.4 larvae/eel in Nakhon Nayok was not significantly different from that of Prachin Buri (9.3 +/- 11.4). A total of 1,292 gnathostome larvae were recovered from 307 eels in Nakhon Nayok. Of these, 52.3% had accumulated in the liver and 47.7% had spread throughout the muscles. In eels from Prachin Buri, 50.6% and 49.4% of the total of 688 larvae (from 308 eels) were found in the liver and muscles, respectively. The larvae preferred encysting in ventral of muscles rather than dorsal part; they preferred the middle portion to the anterior and posterior portions. The average length of gnathostome larvae recovered from Nakhon Nayok eels was 4.0 +/- 0.5 mm (range 2.5-5.1 mm) and the average body width was 0.40 +/- 0.05 mm (range 0.29-0.51 mm). Those from eels in Prachin Buri were 3.9 +/- 0.5 mm (range 2.2-5.1 mm) and 0.34 +/- 0.05 mm (range 0.20-0.48 mm), respectively. The mean body length and width of the larvae from eels in Nakhon Nayok were significantly greater than those of the larvae from eels in Prachin Buri. In Ban Phrao, Nakhon Nayok, none of the first 44 fecal specimens examined was positive. Of the second (68) and the third (70) specimens, one (1.5%) and two (2.9%) samples were positive. However, six months after the third fecal collection, no eggs were found. In Tha Ngam, Prachin Buri, no eggs were found in all three batches (109, 115, and 100 fecal samples). A cyclops survey of 4,000-5,000 crustacea from each of two areas (Ban Phrao and Tha Ngam) found no evidence of natural cyclops infection.

Improved antigens for IgG-ELISA diagnosis of strongyloidiasis.

Two preparations of antigens for the diagnosis of strongyloidiasis were prepared from an extract of the infective larvae of Strongyloides stercoralis: a crude antigen (CA) and a molecular weight cut-off antigen (MWCOA). Both antigens were analysed by indirect ELISA against the sera of strongyloidiasis (26 cases), other helminthiases (167) and normal controls (30). The larvae were obtained from fecal culture by a modified polyethylene tube technique after screening tests by triple simple smears per case. The larvae were extracted with distilled water and further sonicated to obtain a supernatant, the CA. A part of the CA was separated for an antigen containing molecules of lower than 30 kDa by an ultrafree-MC centrifugal filter tube (PLTK): this was designed as the MWCOA. The CA gave 96.15% sensitivity and 40.12% (67/167) specificity at a cut-off value of 0.980 (5SD); false positives were produced by 19 of 20 different helminthiases. The MWCOA produced 96.15% sensitivity at cut-off value of 0.71 (4SD); the specificity of the test was 78.44% (131/167), higher than that of CA. False positives also appeared with 15 other helminthic infections. This study suggests that MWCOA is more specific than CA. A purified MWCOA will be necessary in order to reduce cross-reactivity and provide the suitable diagnosis of strongyloidiasis.