Low Prevalence of Cysticercosis and Trichinella Infection in Pigs in Rural Cambodia

Cysticercosis and Trichinella spp. infection are parasitic zoonoses prevalent among pigs in Southeast Asia, where pork is the most important source of meat. In rural Cambodia, many pigs are raised extensively in family backyards, and information regarding the prevalence in rural small-scale pig production is very limited. This study was conducted in four provinces in north-eastern Cambodia to determine the seroprevalence of porcine cysticercosis and Trichinella spp. infection in rural villages, and to identify possible risk factors. Only households with less than 10 pigs above three months old were eligible. In total, 139 households participated, and 242 blood samples were collected. Farmers were interviewed about food and hygiene habits, disease knowledge and practices. The serum samples were analysed by ELISA to determine antigens to Taenia spp. cysticerci or antibodies to Trichinella spp. muscle larvae. Positivity among the pigs was 11.2% (95% CI 7.5–15.8) for Taenia spp. cysts and 2.5% (95% CI 0.9–5.4) for Trichinella spp. Cysticerci were more common in the province Preah Vihear (p < 0.001) than in the other provinces. Risk factors associated with porcine cysticercosis were management systems for the pigs and access to human faeces (p < 0.001). Trichinella spp. infection in pigs was more common in the province Ratanakiri (p = 0.001). The main risk factor associated with Trichinella spp. transmission was feeding pigs with food waste (p = 0.048). More men had heard about cysticercosis than women (p = 0.002), and men also consumed undercooked pork meat to a greater extent (p = 0.004). Although the present study is relatively small, several risk factors could be identified for porcine infection with Taenia spp. and Trichinella spp., which can be used to guide future interventions to improve both porcine and human health in these provinces.

Japanese Encephalitis in Small-Scale Pig Farming in Rural Cambodia: Pig Seroprevalence and Farmer Awareness

Japanese encephalitis (JE) is endemic in Cambodia, but circulation of JE virus (JEV) among domestic pigs has previously only been studied in the southern part of the country. The main purpose of this study was to determine the seroprevalence of JEV antibodies in smallholder pigs held in rural areas of Kampong Thom, Preah Vihear, Ratanakiri, and Stung Treng provinces, northeastern Cambodia. Another purpose was to identify possible associations between serologic status and other factors, such as reproductive disorders, and to investigate the farmers’ knowledge of mosquito-borne diseases and use of preventive measures. In October 2019, 139 households were visited throughout the study area, and 242 pigs were sampled for blood. The sera were analysed with ELISA for JEV antibodies. Household representatives were interviewed, and data were recorded for each sampled pig. The apparent seroprevalence was 89.1% in pigs between 3 and 6 months of age, and 100% in pigs over 6 months of age. In total, 93.0% of the pigs tested positive. Province appeared to be the only factor significantly associated with serologic status (p < 0.001). Almost all (97.8%) respondents knew that mosquitos could transmit diseases, and 70.5% had heard of JE. However, only one respondent knew that JEV is transmitted to people through mosquito bites. Very few respondents knew that pigs can become infected with JEV, and no one knew that mosquitos transmit the virus. All families used some sort of mosquito protection for themselves, but only 15.1% protected their pigs from mosquito bites. The children were vaccinated against JE in 93 households, while adults only were vaccinated in eight households. The results suggest that JEV transmission is intense in northeastern Cambodia, and that people’s knowledge about the transmission route of JEV and the role of pigs in the transmission cycle is low. Fortunately, people are well aware of mosquito-borne diseases in general and use mosquito protection, and many children are vaccinated against JE. Nonetheless, it is important that national vaccination is continued, and that people—especially in rural areas where pigs are commonly kept—are educated on the ecology and transmission of JEV.

Occurrence of a Hybrid Between Taenia saginata and Taenia asiatica Tapeworms in Cambodia

Human infection with <i>Taenia asiatica</i> or a hybrid between <i>Taenia saginata<i> and <i>T. asiatica</i> has not been reported in Cambodia. We detected for the first time a hybrid form between <i>T. saginata</i> and <i>T. asiatica</i> in Preah Vihear Province, Cambodia. An adult tapeworm specimen, i.e., 75 cm long strobila without scolex, was expelled from a 27-year-old man after praziquantel medication and purging. It was morphologically indistinguishable between <i>T. saginata</i> and <i>T. asiatica</i>. Several proglottids were molecularly analyzed to confirm the tapeworm species. The mitochondrial gene encoding cytochrome <i>c</i> oxidase subunit 1 (<i>cox</i>1) and nuclear genes encoding elongation factor-1α (<i>ef1</i>) and ezrin-radixin-moesin (ERM)-like protein (<i>elp</i>) were sequenced, and a single-allele analysis was performed to confirm the haploid genotype. The results revealed that our sample showed a discrepancy between the mitochondrial and 2 nuclear genes. It possessed homozygous sequences typical of <i>T. saginata</i> at <i>cox</i>1 and <i>ef1</i> loci. However, it was heterozygous at the <i>elp</i> locus, with 1 allele in <i>T. asiatica (elpA)</i> and 1 in <i>T. saginata (elpC</i>), which indicates that it is a hybrid between <i>T. saginata</i> and <i>T. asiatica</i>. The present results confirmed the presence of a hybrid between <i>T. saginata</i> and <i>T. asiatica</i> in Cambodia and strongly suggest the existence of also ‘pure’ <i>T. asiatica</i> in Cambodia.

Morphological and Molecular Diagnosis of Necator americanus and Ancylostoma ceylanicum Recovered from Villagers in Northern Cambodia

Human hookworm infections caused by adult <i>Ancylostoma</i> spp. and <i>Necator americanus</i> are one of the most important tropical diseases. We performed a survey of intestinal helminths using the Kato-Katz fecal examination technique targeting 1,156 villagers residing in 2 northern provinces (Preah Vihear and Stung Treng) of Cambodia in 2018. The results revealed a high overall egg positive rate of intestinal helminths (61.9%), and the egg positive rate of hookworms was 11.6%. Nine of the hookworm egg positive cases in Preah Vihear Province were treated with 5-10 mg/kg pyrantel pamoate followed by purging with magnesium salts, and a total of 65 adult hookworms were expelled in diarrheic stools. The adult hookworms were analyzed morphologically and molecularly to confirm the species. The morphologies of the buccal cavity and dorsal rays on the costa were observed with a light microscope, and the nucleotide sequences of mitochondrial cytochrome <i>c</i> oxidase subunit 1 (<i>cox</i>1) gene were analyzed. The majority of the hookworm adults (90.7%) were <i>N. americanus</i>, whereas the remaining 9.3% were <i>Ancylostoma ceylanicum</i>, a rare hookworm species infecting humans. The results revealed a high prevalence of hookworm infections among people in a northern part of Cambodia, suggesting the necessity of a sustained survey combined with control measures against hookworm infections.