Thai koi-hoi snail dish and angiostrongyliasis due to Angiostrongylus cantonensis: Effects of food flavoring and alcoholic drink on the third-stage larvae in infected snail meat.

Human infection with the rat lungworm Angiostrongylus cantonensis (Parastrongylus cantonensis) in Thailand, especially in the northeastern region, is associated with the habit of eating koi-hoi, which contains raw snail meat. Infection results from the snails being carriers of the larval parasite. The present study was conducted to assess the effect of food flavorings in koi-hoi, alcohol, and exposure time of the two variable on the infective larvae of A. cantonensis. Infected Biomphalaria glabrata snails were used for koi-hoi preparation. Raw snail meat was mixed with koi-hoi flavoring and left at room temperature for various time periods ranging from 5 to 60 minutes. At a predetermined time, two pieces of snail meat were removed at random and examined for viability (as determined by motility) of the parasitic third-stage larvae. At the same time, two random pieces of snail meat were removed and treated with 10 mL of a local 40% alcoholic drink for 30 minutes before examination of larval viability. Exposure of infected snail meat for 10 minutes or more to koi-hoi food flavoring resulted in significantly more nonmotile (dying or dead) larvae. Addition of the local alcoholic drink after exposure to the flavoring exerted an additional killing effect on the larvae. Despite long exposure time, both the koi-hoi flavoring and addition of alcoholic drink were not completely effective in killing the infective larvae in the snail meat. Thorough cooking of the food intended for human consumption should still be practiced.

Laboratory evaluation of aromatic essential oils from thirteen plant species as candidate repellents against Leptotrombidium chiggers (Acari: Trombiculidae), the vector of scrub typhus.

Scrub typhus, a rickettsial disease transmitted by several species of Leptotrombidium chiggers (larvae), is endemic in many areas of Asia. The disease is best prevented by the use of personal protective measures, including repellents. In this study commercially produced aromatic, essential oils of 13 plant species and ethanol (control) were tested in the laboratory for repellency against host-seeking chiggers of Leptotrombidium imphalum Vercammen-Grandjean and Langston (Acari: Trombiculidae). A rapid, simple and economic in vitro test method was used by exposing the chigger for up to 5 min. Repellency was based on relative percentages of chiggers attracted to test and control substances. Four of the 13 essential oils showed promise as effective repellent against L. imphalum chiggers. Syzygium aromaticum (clove) oil exhibited 100% repellency at 5% concentration (dilution with absolute ethanol), whereas Melaleuca alternifolia (tea tree) oil exhibited 100% repellency at 40% concentration. Undiluted oils of Zingiber cassamunar (plai) and Eucalyptus globules (blue gum) exhibited 100% repellency. Of the remaining nine essential oils, only 100% Pelargonium graveolens (geranium) exhibited >50% repellency (viz. 57%). Styrax torkinensis (benzoin) oil did not exhibit any repellency. These findings show that several aromatic, essential oils of plants may be useful as chigger repellent for the prevention of scrub typhus. Syzygium aromaticum oil may be safer and more economical to prevent chigger attacks than commercially available synthetic chemicals, such as DEET that may have harmful side effects.

Mammomonogamus roundworm (Nematoda: Syngamidae) recovered from the duodenum of a Thai patient: a first and unusual case originating in Thailand.

A pair of Mammomonogamus laryngeus roundworms in copula was recovered from the duodenum of a 72-year-old male Thai patient from Kanchanaburi Province. Eggs were also found in the stool of the patient. This is the first case of Mammomonogamus infection originating in Thailand, as the previous two reports from Thailand attributed the infection as originating in Malaysia. The occurrence of adult worms in the duodenum is unusual and differs from previous findings in the larynx, posterior pharynx, tracheal wall and bronchi. This adds a new dimension to the manifestation of the infection.

Parafilaria bovicola Tubangui 1934 from a human eye in Thailand.

A 72 year old Thai male; a resident of Kapoe district, Ranong Province, Southern Thailand presented with conjunctivitis of the left eye. A filariid nematode was recovered from under the medial side of ocular conjunctiva of the left eye. The filariid nematode was identified as a young adult female Parafilaria bovicola, based on the following characteristics: no alteration of the transverse striations on the anterior end of the body, the terminal anus and the vulva opening is just posterior to the mouth. This is a first case report in Thailand of P bovicola causing human disease. P. bovicola has caused damage to the meat industry in many countries and has caused disease in humans. Further study of the life cycle, occurrence among cattle, and transmission of the disease between it's natural host and humans is necessary.

Blinded multi-laboratory evaluation of an in-house dot-blot ELISA kit for diagnosis of human parastrongyliasis.

An in-house membrane dot-blot enzyme-linked immunosorbent assay kit, for the detection of specific antibody to a 31 kDa protein of Parastrongylus cantonensis was evaluated in a blinded multi-laboratory study. The kit was provided to technologists, who were trained in its use, from nine regional laboratories of Thailand. With an identical set of 20 coded serum samples and reference positive and negative controls, the kit was found to have a diagnostic sensitivity of 100% and a diagnostic specificity of 100% in all the laboratories. There was no obvious variation in quality among five lots of the antigen-coated nitrocellulose strips evaluated. The shelf life of the kit was > or = 6 months when the test components were stored at 4 degrees C and 18 months at -20 degrees C. The enzyme-linked immunoassay dot technique is easy to perform and does not require sophisticated electrical equipment; the result is available within 3 hours. If appropriate technical training is included, the application of this dot-blot ELISA kit in clinical laboratories throughout Thailand should be possible.

Effect of Thai 'koi-hoi' food flavoring on the viability and infectivity of the third-stage larvae of Angiostrongylus cantonensis (Nematoda: Angiostrongylidae).

The effect of the food flavoring of 'koi-hoi', a popular Thai snail dish, on the viability and infectivity of Angiostrongylus (=Parastrongylus) cantonensis third-stage larvae was assessed in a mouse model. Groups of 50 each of actively moving, non-motile coiled, and extended larvae were obtained from experimentally infected snail meat, after one-hour exposure to standard 'koi-hoi' flavoring. These larvae and groups of 50 unexposed moving larvae (control) were individually fed to each group of three experimental BALB/c mice. The effect on Angiostrongylus worm burden was measured after 3 weeks of infection. Infectivity of the motile larvae after exposure to 'koi-hoi' food flavoring was 38 + or - 5.29%. This was highly significantly lower than the infectivity (62 + or - 7.21%) of the control (unexposed) third-stage larvae (chi(2) = 17.28, P < 0.001). In the non-motile larvae resulting from exposure to the food flavoring, no adult worm was recovered from the extended larvae, indicating that they were no longer alive and unable to cause infection. A small proportion (3.33 + or - 2.31%) of the coiled larvae developed into young adult worms, indicating that mobility alone is not a definitive indicator of viability. The present study confirms that the food flavoring components of 'koi-hoi' dish adversely affect the viability and infectivity of A. cantonensis larvae. Exposure of the third-stage larvae to 'koi-hoi' food flavoring resulted in decreased viability and eventually death. Prolonged treatment with food flavoring to inactivate/immobilize and then kill the infective, third-stage larvae of A. cantonensis in snail meat prior to consumption may be one of the possible economical means of reducing human infection.