The Journal of Tropical Medicine and Parasitology

Role of Cathepsin B in Schistosoma japonicum Infection

Saiwasan Buathong

Proteases, including cysteine-, serine-, threonine-, aspartate-, and metallo-proteases, are a group of enzymes that have the catalytic ability to hydrolyze or digest peptide bonds of proteins. Proteases play important roles in host invasion, hemoglobin degradation, transformation and immune invasion of schistosomes. The gut cathepsin B of all schistosomes including S. japonicum, S. mansoni and S. haematobuim is involved in hemoglobinolysis. Since Schistosoma japonicum cercariae show quicker migration through host skin as compared to S. mansoni and S. haematobium, it has been proposed that cathepsin B residing in the acetabular gland of S. japonicum might be one of the factors that facilitates its rapid skin penetration. This review focuses on the potential roles of cathepsin B for hemoglobin degradation and skin penetration of schistosomes. Defining the role of cathepsin B might be useful in identifying the drug target for schistosomiasis.

Prevalence of hair follicle mites, Demodex folliculorum and Demodex brevis, on the facial skin of Chiang Mai University Students, and the relationship with acne vulgaris

Atipat Manoyana

The hair follicle mites, Demodex folliculorum and D. brevis are asymptomatic parasites of humans. To date, the genus Demodex has been implicated in the occurrence of many skin diseases. Thus, the main aim of this study was to determine the infestation rate of Demodex spp. in young adults and study the relationship between Demodex density and acne vulgaris. Furthermore, the mean densities of Demodex mites between clindamycin users and a control group were also observed in this study. Studied population consisted of 280 healthy volunteers from Chiang Mai University (age 20-22 years old). Skin samples were collected by a skin scraping technique and were examined for the parasite by direct microscopic examination. Both species were found in the resulting skin samples. The overall prevalence of Demodex mites on the facial skin of Chiang Mai University students was 40.36%. The mite prevalence in males (44.20%) was significantly higher than in female (36.62%) (P = 0.024). Demodex folliculorum had a higher prevalence (31.1%) than D. brevis (26.1%). The mite density in males (0.89 Demodex/cm2) was also significantly higher than in female (0.49 Demodex/cm2) (P = 0.035). We also found that males were approximately twice as likely to have acne vulgaris as females. Although Demodex has been involved in the etiology of many skin diseases, the parasite does not appear to be related to acne vulgaris in young adults (P = 0.313). Thus, the eradication of Demodex mites is not necessary for the therapeutic treatment of acne vulgaris. The mites were found on all facial sites, the highest density being in the area of the nose followed by the forehead and cheeks, but there was no significant difference among these 3 areas. This study also determined the effect of clindamycin on Demodex mites. The results revealed that the use of clindamycin was not related to the density of Demodex mites. However, additional sample sizes for the clindamycin study are needed.

Refractoriness of the natural malaria vector Culex quinquefasciatus to Plasmodium gallinaceum

Mintra Pruck-Ngern

Development of effective strategies to control malaria transmission is an important issue in malaria research. This study aimed to investigate refractoriness of laboratory and field strains of the malaria vector Culex quinquefasciatus to the avian malaria parasite Plasmodium gallinaceum, a model of the human malaria disease. Transmission potential was determined by feeding batches of Cx. quinquefasciatus on P. gallinaceum infected chickens with 10% and 30% parasitemia. The mosquitoes were examined for percent infectivity and numbers of oocysts. Our study showed that when the mosquitoes were fed on the infected chickens with high parasitemia, the laboratory isolate of Cx. quinquefasciatus was more susceptible to P. gallinaceum transmission and produced significantly higher oocyst numbers than the field isolate. There were, however, no differences in term of the transmission potential and infectivity of the malaria parasite when the mosquitoes were allowed to feed on the P. gallinaceum-infected chickens with low parasitemia. In conclusion, our study demonstrated the differences in refractoriness of the natural vector Cx. quinquefasciatus to the transmission of the avian malaria P. gallinaceum, implying the existence of the natural pathogen resistance mechanisms in the Culex mosquito.

Intestinal parasites in captive mugger crocodiles (Crocodylus palustris) in south India

NV Rajesh

Coprological samples of captive mugger crocodiles (Crocodylus palustris) were randomly collected (N=102) from Snake Park, Guindy (N=36), Arignar Anna Zoological Park, Vandalur (N=44) and Amaravathy Crocodile farm (N=22) and screened for evidence of intestinal parasites using fecal sedimentation and flotation technique. Quantitative analysis of fecal samples was not performed for this study. The fecal samples collected were on random sampling basis under captive environment condition, irrespective of their sex, since both male and female are reared in the confined area. The samples were collected among the adult group of crocodiles (> 8 ft) in length bearing an average weight of 500 pounds. Parasitic fauna evidenced trematode eggs including Renifers which were predominant in Snake Park, Guindy (36.1%) and Amaravathy Crocodile farm (22.7%), and nematode eggs, Dujardinascaris sp., in Arignar Anna Zoological Park, Vandalur (36.4%). There were mixed infection between Dujardinascaris sp., (11.4%) and Renifers (5.6%). Ophiotaenia sp. was also found in a few samples. Polydelphis sp. was found in Amaravathy farm (13.7%). Renifers (19.6%) and Dujardinascaris sp. (21.6%) were found in mugger crocodiles from all these three locations. Mixed infection of sporulated coccidian oocyst (4.9%) Isospora sp. and Eimeria sp. were found in Snake Park Guindy and Amaravathy Crocodile farm. Snake Park, Guindy and Amaravathy Crocodile farm had the habit of feeding fishes to this crocodile resulting in the transmission of trematode and cestode.