Restoration of hookworm egg development after prolonged storage in stool suspension

Hookworm infection is still prevalent in southern Thailand despite control measures. Hookworm eggs submerged for an extended period under water from rainfall or in latrines may not survive, but they may recover their ability to develop into infective larvae when exposed to atmospheric air. This study examined the survival of the hookworm eggs in stool suspension and the restoration of development capability after prolonged storage. In stool mass, eggs developed normally and yielded infective filariform larvae (FL) in 7 days. On the contrary, in 1:10 stool suspension, hookworm eggs were found to remain at the 4-8 cell stage; degenerated eggs were observed after 15 days of storage, and the number of degenerated eggs reached 80 % on day 30. Aeration of the suspension, or transferring to a Petri dish or agar plate, restored the capacity of eggs stored for up to 15 days to develop into FL; thereafter, the capacity declined sharply. Retardation of egg development under water or in stool suspension may be due to a lack of atmospheric air. Use of "night soil" from latrines as fertilizer may be one factor in maintaining hookworm transmission, as worm eggs can undergo normal development upon exposure to atmospheric air.

The majority of cockroaches from the Samutprakarn province of Thailand are carriers of parasitic organisms

We undertook a study of the mechanical transmission of parasitic organisms in cockroaches in the Samutprakarn province of Thailand. In this study, 920 cockroaches were obtained from 18 open-air shopping markets in 5 districts and 1 subdistrict of this province. All cockroaches were captured during their feeding time in their natural habitat. Direct wet smear and modified acid-fast bacilli staining were used to identify the parasites from the external surface or cuticle of the cockroaches. The results show that 498 (54.1 %) of the cockroaches harbored parasitic organisms. Of these, 56.1 % were protozoa and the remaining 43.9 % were helminthes (pathogenic helminthes- 1.4 %, non-pathogenic helminthes- 42.5 %). Of the pathogenic helminthes, the species included Strongyloides stercoralis (6 instances of the free-living adult male, 0.8 %), Ascaris lumbricoides (2 decorticated eggs, 0.3 %), Trichuris trichiura (2, 0.3 %), and Taenia spp. (1 egg, 0.1 %). The protozoa types that were identified included Cyclospora spp. (10 oocysts, 1.3 %), Endolimax nana (10 cysts, 1.3 %), B. hominis (9 instances of the vacuolated form, 1.2 %), Isospora belli (75 oocysts, 9.6 %), Entamoeba histolytica/E. dispar (36 cysts, 4.6 %), Cryptosporidium spp. (220 oocysts, 28.1 %), Chilomastix mesnilli (2 cysts, 0.3 %), Entamoeba coli (31 cysts, 4.0 %), Balantidium coli (45 trophozoites, 5.8 %), and Iodamoeba butschlii (1 cyst, 0.1 %). These results show that cockroaches isolated from these markets are carriers of several parasitic organisms that cause commonly found symptoms of illness such as diarrhea or bowel disorder.