Genetic diversity and population structure of Plasmodium falciparum in the Philippines

<p>Abstract</p> <p>Background</p> <p>In the Philippines, malaria morbidity and mortality have decreased since the 1990s by effective malaria control. Several epidemiological surveys have been performed in the country, but the characteristics of the <it>Plasmodium falciparum </it>populations are not yet fully understood. In this study, the genetic structure of <it>P. falciparum </it>populations in the Philippines was examined.</p> <p>Methods</p> <p>Population genetic analyses based on polymorphisms of 10 microsatellite loci of the parasite were conducted on 92 isolates from three provinces (Kalinga, Palawan, and Davao del Norte) with different malaria endemicity.</p> <p>Results</p> <p>The levels of genetic diversity and the effective population sizes of <it>P. falciparum </it>in the Philippines were similar to those reported in the mainland of Southeast Asia or South America. In the low malaria transmission area (Kalinga), there was a low level of genetic diversity and a strong linkage disequilibrium (LD) when the single-clone haplotype (SCH) was used in the multilocus LD analysis, while in the high malaria transmission areas (Palawan and Davao del Norte), there was a high level of genetic diversity and a weak LD when SCH was used in the multilocus LD analysis. On the other hand, when the unique haplotypes were used in the multilocus LD analysis, no significant LD was observed in the Kalinga and the Palawan populations. The Kalinga and the Palawan populations were, therefore, estimated to have an epidemic population structure. The three populations were moderately differentiated from each other.</p> <p>Conclusion</p> <p>In each area, the level of genetic diversity correlates with the local malaria endemicity. These findings confirm that population genetic analyses using microsatellite loci are a useful tool for evaluating malaria endemicity.</p

Field Evaluation of Recombinant Antigen ELISA in Detecting Zoonotic Schistosome Infection Among Water Buffaloes in Endemic Municipalities in the Philippines

In this study, we investigated the use of recombinant antigens thioredoxin peroxidase-1 (rSjTPx-1) and tandem repeat rSj1TR in evaluating the antibody positivity rates of Schistosoma japonicum infection among water buffaloes from four endemic areas in the Philippines, two municipalities with high endemicity (Calatrava, Negros Occidental and Catarman, Northern Samar) and two municipalities nearing elimination with no cases of human schistosomiasis (Talibon and Trinidad, Bohol). These recombinant antigen ELISA assays were compared with other diagnostic tests including SEA-ELISA, FECT, and fecal-based PCR. Results showed that rSj1TR-ELISA has the highest agreement with PCR in all study areas. Furthermore, significant positivity rates among water buffaloes were seen in Talibon and Trinidad, indicating that water buffaloes are maintaining the schistosome parasites in transmission areas even in the absence of human infection. Hence, serological assay using a more sensitive and specific rSj1TR-ELISA can be used for animal surveillance to prevent emergence and re-emergence of human schistosomiasis

Mapping the Risk of Soil-Transmitted Helminthic Infections in the Philippines

The authors thank the regional coordinators, regional directors, provincial health officers, provincial health team leaders, municipal health officers, medical technologists, midwives, and barangay health workers for their commitment, which was key to completing all the phases of the national prevalence survey. We would like to thank Prof. May Lebanan for assisting us in the preparation of the data set.Author Summary Soil-transmitted helminth (STH) infections with A. lumbricoides, T. trichiura and hookworms are endemic in all 80 provinces of the Philippines, but the spatial variation in the prevalence of these infections has not been previously described. This analysis revealed that while A. lumbricoides and T. trichiura infections were widespread and highly endemic, hookworm infections were more circumscribed to smaller foci in the Visayas and Mindanao. The results also suggest that it may be necessary to place greater emphasis on improving the provision of water, sanitation and the promotion of behavioral change for improved hygiene for the control and prevention of STH infections, particularly for hookworm.Yeshttp://www.plosntds.org/static/editorial#pee

Geographical information systems in health research and services delivery in the Philippines

Accessible public data emanating from remote sensing from earth-observing satellites, as well as geographical information systems in general, are playing an increasing role in the public health sector in the Philippines. This paper reviews currently available systems in the country in this area, emphasizing the utility in complementing field studies with the development of disease models. The goal is to map out important biological threats by characterizing the niches infectious agents, and their vectors or intermediate hosts, occupy temporally and spatially

Utilization of ELISA using thioredoxin peroxidase-1 and tandem repeat proteins for diagnosis of Schistosoma japonicum infection among water buffaloes.

BACKGROUND: The presence of animal reservoirs in Schistosoma japonicum infection has been a major obstacle in the control of schistosomiasis. Previous studies have proven that the inclusion of control measures on animal reservoir hosts for schistosomiasis contributed to the decrease of human cases. Animal surveillance should therefore be included to strengthen and improve the capabilities of current serological tests. METHODOLOGY/PRINCIPAL FINDINGS: Thioredoxin peroxidase-1 (SjTPx-1) and four tandem repeat proteins (Sj1TR, Sj2TR, Sj4TR, Sj7TR) were initially evaluated against human sera. The previous test showed high sensitivity and specificity for antibody detection against SjTPx-1 and Sj7TR. In this study, the immunodiagnostic potential of these recombinant proteins was evaluated using enzyme-linked immunoassay on 50 water buffalo serum samples collected in Cagayan, the Philippines as compared with the soluble egg antigen (SEA). For specificity, 3 goat serum samples positive with Fasciola hepatica were used and among the antigens used, only SEA showed cross-reaction. Stool PCR targeting the S. japonicum 82 bp mitochondrial NAD 1 gene was done to confirm the true positives and served as the standard test. Twenty three samples were positive for stool PCR. SjTPx-1 and Sj1TR gave the highest sensitivity among the recombinant proteins tested for water buffalo samples with 82.61% and 78.26% respectively which were higher than that of SEA (69.57%). CONCLUSIONS/SIGNIFICANCE: These results prove that SjTPx-1 works both for humans and water buffaloes making it a good candidate antigen for zoonotic diagnosis. Sj1TR showed good results for water buffaloes and therefore can also be used as a possible candidate for detecting animal schistosome infection

Detection of canine Schistosoma japonicum infection using recombinant thioredoxin peroxidase-1 and tandem repeat proteins

Humans and dogs live very close together and share various pathogens causing zoonotic parasitoses like schistosomiasis. A previous population genetics study done for schistosomes in the Philippines suggested that there is a high transmission level of Schistosoma japonicum among humans and dogs proving that the latter are important reservoirs for this zoonotic parasite. A more sensitive and specific test detecting schistosome infection in dogs will therefore strengthen the zoonotic surveillance, which might help in the possible elimination of this ancient disease. In this study, recombinant thioredoxin peroxidase-1 (SjTPx-1) and tandem repeat proteins (Sj1TR, Sj2TR, Sj4TR, Sj7TR) previously tested on human and water buffalo samples were used to assess its diagnostic applicability to dogs. Fifty-nine dog serum and stool samples were collected in the schistosomiasis-endemic municipalities of Calatrava, Negros Occidental and Catarman, Northern Samar in the Philippines and examined using the ELISA as compared to microscopy and fecal sample-based PCR. Samples positive for Babesia gibsoni and Dirofilaria immitis were also used to check for cross-reaction. Results showed that SjTPx-1 (80% sensitivity, 92.3% specificity) and Sj7TR (73.3% sensitivity, 92.3% specificity) have good potentials for diagnosing S. japonicum infection in dogs. These diagnostic antigens will therefore improve the surveillance in the transmission of the parasites from dogs to humans