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

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

Patient Knowledge on Malaria Symptoms Is a Key to Promoting Universal Access of Patients to Effective Malaria Treatment in Palawan, the Philippines

<div><p>Introduction</p><p>Palawan, where health care facilities are still limited, is one of the most malaria endemic provinces in the Philippines. Since 1999, microscopists (community health workers) have been trained in malaria diagnosis and feasibility of early diagnosis and treatments have been enhanced throughout the province. To accelerate the universal access of malaria patients to diagnostic testing in Palawan, positive health seeking behavior should be encouraged when malaria infection is suspected.</p><p>Methods</p><p>In this cross-sectional study, structured interviews were carried out with residents (N = 218) of 20 remote malaria-endemic villages throughout Palawan with a history of suspected malaria from January to February in 2012. Structural equation modeling (SEM) was conducted to determine factors associated with appropriate treatment, which included: (1) socio-demographic characteristics; (2) proximity to a health facility; (3) health seeking behavior; (4) knowledge on malaria; (5) participation in community awareness-raising activities.</p><p>Results</p><p>Three factors independently associated with appropriate treatment were identified by SEM (CMIN = 10.5, df = 11, CFI = 1.000, RMSEA = .000): “living near microscopist” (<i>p</i> < 0.001), “not living near private pharmacy” (<i>p</i> < 0.01), and “having severe symptoms” (<i>p</i> < 0.01). “Severe symptoms” were positively correlated with more “knowledge on malaria symptoms” (<i>p</i> < 0.001). This knowledge was significantly increased by attending “community awareness-raising activities by microscopists” (<i>p</i> < 0.001).</p><p>Conclusions</p><p>In the resource-limited settings, microscopists played a significant role in providing appropriate treatment to all participants with severe malaria symptoms. However, it was considered that knowledge on malaria symptoms made participants more aware of their symptoms, and further progressed self-triage. Strengthening this recognition sensitivity and making residents aware of nearby microscopists may be the keys to accelerating universal access to effective malaria treatment in Palawan.</p></div

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

Map of Annual Parasite Incidence (API) (confirmed infections/1,000 population at risk) by municipalities, 2010.

<p>This map was constructed by the authors based on the data of provincial health report 2010 [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0127858#pone.0127858.ref005" target="_blank">5</a>].</p

Nominal socio-economic status variables of participants with respect to first treatment sought.

<p>¹Fisher’s exact test between first treatment sought.</p><p>Nominal socio-economic status variables of participants with respect to first treatment sought.</p

Correlation matrix.

<p>* Significant difference (0.01 < <i>p</i> < 0.05),</p><p>** Significant difference (0.001 < <i>p</i> < 0.01),</p><p>*** Significant difference (<i>p</i> < 0.001).</p><p>Correlation matrix.</p

Proximity to health facility, symptoms, and awareness-raising activities of the participants with respect to first treatment sought (multiple answers allowed).

<p>¹Fisher’s exact test between first treatment sought.</p><p>*Significant difference (0.01 ≤ <i>p</i> < 0.05),</p><p>**Significant difference (0.001 ≤ <i>p</i> < 0.01),</p><p>***Significant difference (<i>p</i> < 0.001).</p><p>Proximity to health facility, symptoms, and awareness-raising activities of the participants with respect to first treatment sought (multiple answers allowed).</p

Continuous socio-economic status variables of participants with respect to first treatment sought.

<p>¹ANOVA between first treatment sought.</p><p>²This scale scores from 1–8 points, with 1 point each for each of the following: electricity, radio, television, refrigerator, bicycle, motorcycle, bike-car, and tin or cement wall.</p><p>Continuous socio-economic status variables of participants with respect to first treatment sought.</p