The disease state of amebiasis, caused by Entamoeba histolytica, varies from asymptomatic to severe manifestations that include dysentery and extraintestinal abscesses. The virulence factors of the pathogen, and host defense mechanisms, contribute to the outcomes of infection; however, the underlying genetic factors, which affect clinical outcomes, remain to be fully elucidated. To identify these genetic factors in E. histolytica, we used Illumina next-generation sequencing to conduct a comparative genomic analysis of two clinical isolates obtained from diarrheal and asymptomatic patients (strains KU50 and KU27, respectively). By mapping KU50 and KU27 reads to the genome of a reference HM-1:IMSS strain, we identified two genes (EHI_089440 and EHI_176590) that were absent in strain KU27. In KU27, a single AIG1 (avrRpt2-induced gene 1) family gene (EHI_176590) was found to be deleted, from a tandem array of three AIG1 genes, by homologous recombination between the two flanking genes. Overexpression of the EHI_176590 gene, in strain HM-1:IMSS cl6, resulted in increased formation of cell-surface protrusions and enhanced adhesion to human erythrocytes. The EHI_176590 gene was detected by PCR in 56% of stool samples from symptomatic patients infected with E. histolytica, but only in 15% of stool samples from asymptomatic individuals. This suggests that the presence of the EHI_176590 gene is correlated with the outcomes of infection. Taken together, these data strongly indicate that the AIG1 family protein plays a pivotal role in E. histolytica virulence via regulation of host cell adhesion. Our in-vivo experiments, using a hamster liver abscess model, showed that overexpression or gene silencing of EHI_176590 reduced and increased liver abscess formation, respectively. This suggests that the AIG1 genes may have contrasting roles in virulence depending on the genetic background of the parasite and host environment. Comparative genomic analysis of pathogens is used to identify genes associated with disease manifestations. In the present study, this approach was used to identify genes, present in a strain of Entamoeba histolytica isolated from dysenteric patients, but absent in strains isolated from asymptomatic infected individuals. Strain KU27 is an “avirulent” strain, or less virulent as compared to the virulence of other strains. KU27 was isolated from an asymptomatic infected individual, and is incapable of producing abscesses in a hamster liver abscess model. A previous genotyping study, using tRNA-linked short tandem repeats as markers, also identified this Japanese strain as a genetically distinct low-virulence strain. We conducted a comparative genomic analysis of strain KU27 against virulent strain of E. histolytica. Our analysis identified an AIG1 gene as a potential determinant of virulence. Further, we demonstrated that the gene product is involved in the formation of protrusions on the plasma membrane and adherence to host cells. To the best of our knowledge, this is the first study to identify a virulence-associated gene by comparative genomics. Here, we demonstrate the causal connection of the identified gene with virulence by the analysis of cell morphology, adhesion competence, and distribution among clinical isolates.

Schistosomiasis japonica remains a public health concern in many areas of the Philippines. Adequate and updated information is essential to enhance policy and service delivery toward control and elimination. Despite the efforts on schistosomiasis control in the Philippines, some challenges remain in these dimensions. An integrated surveillance system is recommended to determine the prevalence of infection in humans, animal reservoirs, and snail intermediate hosts, allowing the identification of high-priority areas for targeted interventions. This will entail the enhancement of laboratory diagnosis capacity through the use of more sensitive techniques, complemented by capacity building of concerned human and animal health professionals. Given the zoonotic nature of schistosomiasis japonica, adopting the One Health approach is essential to influence policies and interventions that may accelerate control and elimination. This can be achieved through the attainment of mass drug administration coverage targets and intensified case finding and management, robust implementation and integration of veterinary public health activities, the conduct of snail control measures, provision of safe water, sanitation, and hygiene services, and health promotion and education into the national schistosomiasis control and elimination program. This review aimed to describe the status of schistosomiasis japonica control in the Philippines in the context of human health, animal health, vector ecology and management, environmental health, and sociocultural dimensions.

Background and Aim: Schistosomiasis (SCH) japonica is a zoonotic disease that can infect several mammalian hosts. Bovines, particularly water buffaloes, are considered the most important reservoir hosts due to the high levels of schistosome eggs, they excrete into the environment. In the Philippines, the previous studies have revealed a high prevalence of SCH in bovines in selected provinces in Luzon, Visayas, and Mindanao. However, there is a lack of studies on SCH in the Davao Region, Mindanao, where the infection remains a public health concern. This study aimed to determine the prevalence of SCH in water buffaloes in four barangays (villages) each in Braulio Dujali, Davao del Norte and Maragusan, Davao de Oro, Southeastern Mindanao, the Philippines. Materials and Methods: Fecal samples from 91 water buffaloes were collected intrarectally, processed using the formalin-ethyl acetate sedimentation technique, and examined microscopically to determine the prevalence of SCH. Results: A total of three water buffaloes (8.6%) in Maragusan were determined to be positive for Schistosoma japonicum, while none in Braulio Dujali. The prevalence of other parasites (Fasciola spp. [53.8%], Paramphistome spp. [20.9%], Amphistome spp. [16.5%], Strongyle spp. [11.0%], Balantidium spp. [9.9%], Eurytrema spp. [2.2%], and Gongylonema pulchrum [1.1%]) was also observed. Conclusion: The results of the study provide baseline data on the presence of S. japonicum in water buffaloes in the Davao Region, Mindanao. Strategies for controlling and eliminating SCH in animal reservoir hosts, especially in water buffaloes, are necessary for the long-term control and elimination of SCH in humans.

Paragonimus westermani is a food-borne zoonotic trematode transmitted to humans through the consumption of undercooked crustaceans. Freshwater crabs act as the second intermediate host for the encysted metacercariae stage. However, accurate identification of intermediate hosts remains a challenge. Here, we aimed to detect and identify P. westermani in randomly collected freshwater crabs and determine the species of infected crabs in Davao Oriental through molecular methods. Specifically, Sanger and next-generation sequencing were conducted for species identification through BLASTn, followed by phylogenetic analyses to understand geographic and taxonomic relationships. Results showed P. westermani DNA was detected in five out of eleven crab samples and these sequences were closely grouped to the Philippine reference sequence. Through a similar approach, the infected crabs showed high sequence similarity and formed tight clustering to Isolapotamon sp. Overall, the results provided evidence that P. westermani DNA was detected in Isolapotamon sp., a genus endemic to Mindanao, and can be a potential intermediate host. This expands our current understanding of transmission ecology beyond the only known intermediate host in the Philippines, Sundathelphusa philippina.

Emerging infectious diseases due to coronavirus (CoV) infections have received significant global attention in the past decade and have been linked to bats as the original source. The diversity, distribution, and host associations of bat CoVs were investigated to assess their potential for zoonotic transmission. Phylogenetic, network, and principal coordinate analysis confirmed the classification of betacoronaviruses (BetaCoVs) into five groups (2A to 2E) and a potentially novel group, with further division of 2D into five subgroups. The genetic co-clustering of BetaCoVs among closely related bats reflects host taxon-specificity with each bat family as the host for a specific BetaCoV group, potentially a natural barrier against random transmission. The divergent pathway of BetaCoV and host evolution suggests that the viruses were introduced just prior to bat dispersal and speciation. As such, deviant patterns were observed such as for 2D-IV, wherein cross-taxon transmission due to overlap in bat habitats and geographic range among genetically divergent African bat hosts could have played a strong role on their shared CoV lineages. In fact, a few bat taxa especially the subfamily Pteropodinae were shown to host diverse groups of BetaCoVs. Therefore, ecological imbalances that disturb bat distribution may lead to loss of host specificity through cross-taxon transmission and multi-CoV infection. Hence, initiatives that minimize the destruction of wildlife habitats and limit wildlife-livestock-human interfaces are encouraged to help maintain the natural state of bat BetaCoVs in the wild. Importance: Bat Betacoronaviruses (BetaCoVs) pose a significant threat to global public health and have been implicated in several epidemics such as the recent pandemic by severe acute respiratory syndrome coronavirus 2. Here, we show that bat BetaCoVs are predominantly host-specific, which could be a natural barrier against infection of other host types. However, a strong overlap in bat habitat and geographic range may facilitate viral transmission to unrelated hosts, and a few bat families have already been shown to host multi-CoV variants. We predict that continued disturbances on the ecological balance may eventually lead to loss of host specificity. When combined with enhanced wildlife-livestock-human interfaces, spillover to humans may be further facilitated. We should therefore start to define the ecological mechanisms surrounding zoonotic events. Global surveillance should be expanded and strengthened to assess the complete picture of bat coronavirus diversity and distribution and their potential to cause spillover infections.