Dataset Information

Spatial distribution of Taenia solium exposure in humans and pigs in the Central Highlands of Vietnam.

ABSTRACT:

Background

Taenia solium, a pork-borne parasitic zoonosis, is the cause of taeniasis and cysticercosis in humans. In Vietnam, poor sanitation, the practice of outdoor defecation and consumption of raw/undercooked pork have been associated with infection/exposure to T. solium in both humans and pigs. The broad-scale geographic distribution of the prevalence of T. solium varies throughout the country with infection restricted to isolated foci in the north and a more sporadic geographic distribution in the Central Highlands and the south. While cross-sectional studies have allowed the broad-scale geographic distribution of T. solium to be described, details of the geographic distribution of T. solium at finer spatial scales have not been described in detail. This study provides a descriptive spatial analysis of T. solium exposure in humans and pigs and T. solium taeniasis in humans within individual households in village communities of Dak Lak in the Central Highlands of Vietnam.

Methodology/principal findings

We used Ripley's K-function to describe spatial dependence in T. solium exposure positive and negative human and pig households and T. solium taeniasis exposure positive and negative households in villages within the districts of Buon Don, Krong Nang and M'Drak of Dak Lak province in the Central Highlands of Vietnam. The prevalence of exposure to T. solium in pigs in Dak Lak province was 9 (95% CI 5 to 17) cases per 1000 pigs at risk. The prevalence of exposure to the parasite in humans was somewhat higher at 5 (95% CI 3 to 8) cases per 100 individuals at risk. Spatial aggregations of T. solium exposure-positive pig and human households occurred in some, but not all of the villages in the three study districts. Human exposure-positive households were found to be aggregated within a distance of 200 to 300 m in villages in Krong Nang district compared with distances of up to 1500 m for pig exposure-positive households in villages in M'Drak district. Although this study demonstrated the aggregation of households in which either T. solium exposure- or taeniasis-positive individuals were present, we were unable to identify an association between the two due to the very low number of T. solium taeniasis-positive households.

Conclusions

Spatial aggregations of T. solium exposure-positive pig and human households occurred in some, but not all of the villages in the three study districts. We were unable to definitively identify reasons for these findings but speculate that they were due to a combination of demographic, anthropological and micro-environmental factors. To more definitively identify characteristics that increase cysticercosis risk we propose that cross-sectional studies similar in design to that described in this paper should be applied in other provinces of Vietnam.

SUBMITTER: Ng-Nguyen D

PROVIDER: S-EPMC6168177 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Publications

Spatial distribution of Taenia solium exposure in humans and pigs in the Central Highlands of Vietnam.

Ng-Nguyen Dinh D Traub Rebecca Justine RJ Nguyen Van-Anh Thi VT Breen Kathleen K Stevenson Mark Anthony MA

PLoS neglected tropical diseases 20180920 9

<h4>Background</h4>Taenia solium, a pork-borne parasitic zoonosis, is the cause of taeniasis and cysticercosis in humans. In Vietnam, poor sanitation, the practice of outdoor defecation and consumption of raw/undercooked pork have been associated with infection/exposure to T. solium in both humans and pigs. The broad-scale geographic distribution of the prevalence of T. solium varies throughout the country with infection restricted to isolated foci in the north and a more sporadic geographic dis ...[more]

PMID: 30235251

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Project description:BackgroundVietnam is endemic for taeniasis and T. solium cysticercosis. Despite this, information on the epidemiological characteristics of the diseases in the Central Highlands of Vietnam are poorly described. The aims of this study were to determine the epidemiological characteristics of taeniasis (Taenia spp.) and T. solium cysticerci exposure in humans in Dak Lak province in the Central Highlands, Vietnam.MethodsThis cross-sectional study was carried out in six villages in three districts of Dak Lak. A total of 190 households were visited. From each household, between one and five individuals were asked to donate a single faecal and blood sample and respond to a questionnaire. Serum samples were subjected to lentil lectin purified glycoprotein enzyme-linked immunoelectrotransfer blot assay to detect antibodies against T. solium cysticerci. Multiplex real-time PCR was used to detect Taenia spp. infection in faecal samples. A fixed-effects logistic regression model was developed to identify factors associated with the probability of Taenia spp. infection or T. solium cysticerci exposure risk. The contribution of each of identified factor was quantified using population attributable fractions.ResultsThe prevalence of seroexposure to T. solium in Dak Lak was 5% (95% CI 3% to 8%). Consumption of raw vegetables, sourcing drinking water from lakes, streams or ponds and the practice of outdoor defaecation were identified as primary risk factors for the prevalence of T. solium cysticerci exposure, while consuming undercooked pork and beef, pork tongue and observing Taenia proglottids in stool were associated with Taenia spp. infection. Consumption of raw vegetables attributed to 74% of T. solium cysticerci exposure-positive cases and consumption of undercooked beef attributed to 77% of taeniasis cases in these communities.ConclusionsThe prevalence of T. solium seroexposure in Dak Lak is consistent with those reported in other regions of Vietnam. The identified risk factors associated with the prevalence of T. solium seroexposure and taeniasis infection in Dak Lak are modifiable and thus advocate for targeted community intervention programs to mitigating these risks.

Project description:BackgroundTaenia solium, a parasite that affects humans and pigs, is the leading cause of preventable epilepsy in the developing world. Geographic hotspots of pigs testing positive for serologic markers of T. solium exposure have been observed surrounding the locations of human tapeworm carriers. This clustered pattern of seropositivity in endemic areas formed the basis for geographically targeted control interventions, which have been effective at reducing transmission. In this study, we further explore the spatial relationship between human tapeworm carriers and infected pigs using necroscopic examination as a quantitative gold-standard diagnostic to detect viable T. solium cyst infection in pigs.Methodology/principal findingsWe performed necroscopic examinations on pigs from 7 villages in northern Peru to determine the number of viable T. solium cysts in each pig. Participating humans in the study villages were tested for T. solium tapeworm infection (i.e., taeniasis) with an ELISA coproantigen assay, and the distances from each pig to its nearest human tapeworm carrier were calculated. We assessed the relationship between proximity to a tapeworm carrier and the prevalence of light, moderate, and heavy cyst burden in pigs. The prevalence of pig infection was greatest within 50 meters of a tapeworm carrier and decreased monotonically as distance increased. Pigs living less than 50 meters from a human tapeworm carrier were 4.6 times more likely to be infected with at least one cyst than more distant pigs. Heavier cyst burdens, however, were not more strongly associated with proximity to tapeworm carriers than light cyst burdens.Conclusion/significanceOur study shows that human tapeworm carriers and pigs with viable T. solium cyst infection are geographically correlated in endemic areas. This finding supports control strategies that treat humans and pigs based on their proximity to other infected individuals. We did not, however, find sufficient evidence that heavier cyst burdens in pigs would serve as improved targets for geographically focused control interventions.

Project description:BackgroundTaenia solium (T. solium) cysticercosis remains a neglected zoonotic disease in India. The current study was planned to estimate the prevalence of T. solium porcine cysticercosis in the Punjab state of India, to compare this prevalence with the disease prevalence in pigs reared outside Punjab and to assess the distribution of the parasite in pig carcasses.MethodsTwo slaughter shops were selected in each of the 22 districts of Punjab. Pigs slaughtered on the day/s of inspection were post-mortem inspected to identify the presence of T. solium cysts. Estimated true prevalence was estimated by taking into account the diagnostic sensitivity (38%) and specificity (100%) of post-mortem inspection using the Rogan-Gladen estimator. Positive carcasses were purchased and brought to the laboratory to assess the tissue distribution of T. solium cysts and to conduct PCR targeting large subunit rRNA gene, internal transcribed spacer 1 gene, ITS1 gene and Cytochrome oxidase I gene. The selected PCR products were submitted for sequencing and phylogenetic analyses were performed.FindingsWe contacted 71 shop owners to achieve a sample of 44 shops for the study. We inspected 642 pigs reared in Punjab and 450 imported from other states at these slaughter shops. In addition, we sampled 40 pigs from an abattoir located in the state capital. Of the 642 pigs reared in Punjab, 9 had T. solium cysts with an apparent prevalence of 1·40% (95% CI: 0·74%, 2·64%) and the estimated true prevalence of 3.69% (95% CI: 1·95%, 6·95%). Pigs imported from outside the state had a significantly higher prevalence (odds ratio: 2·58; 95% CI: 1·12, 5·98; p-value: 0·026) as 15 of the 450 imported pigs were positive (apparent prevalence: 3.33%; 95% CI: 2.03%, 5.43%; estimated true prevalence: 8.77%; 95% CI: 5.34%, 14.28%). None of samples was positive from the pigs sampled at the abattoir in the state capital. The PCR confirmed T. solium cysts from all the 24 positive samples. We counted a median of 897 (range 526-1964) cysts per infected pig from the 19 infected pig carcasses inspected. The phylogenetic tree based on the alignment of partial cytochrome oxidase 1 sequences indicated all positive samples to be clustered with the T. solium Asian genotype. The analysis did not indicate the presence of T. asiatica in the slaughter pigs.ConclusionsDespite the underestimation of the prevalence due to missing mildly-infected carcasses, low participation and lack of representative sampling, the presence of heavily infected carcasses containing viable cysts, particularly those imported from outside the state, indicates that T. solium cysticercosis is an important food safety concern for pork consumers in Punjab, India. Measures should be taken to reduce the disease prevalence in pigs to reduce the disease burden in the public.

Project description:BackgroundEstimating the burden of neglected tropical diseases is a valuable tool to support policymakers in the resource allocation for control and elimination of these diseases. Spatial analysis allows to identify the geographical distribution patterns of infectious and parasitic diseases within a country and allows to assess their possible correlation with other health disorders. Despite being neurocysticercosis (NCC) considered as the most important parasitic disease of the nervous system, few efforts have been addressed to assess the real burden of NCC in endemic countries, to date, there are no studies estimating the burden of NCC in South America. In this study we aimed to use the Disability Adjust Life Years (DALY) and spatial indicators as tools to measure the impact of human neurocysticercosis in Ecuador between 2013 and 2017.MethodsMortality, morbidity and spatial data from the national agency of statistics were used to estimate the burden of disease of NCC during a five-year period (2013-2017). NCC cases and its two main sequelae, epilepsy and migraine headache, were stratified by sex and age group to calculate the DALY associated to NCC using the DALY package in R. SATSCAN software was used to assess spatial clusters of NCC and its possible neurological sequelae as epilepsy, status epilepticus, migraine and hydrocephalus.Principal findingsThe burden of human neurocysticercosis ranged from 56201 [95% CI 29961-89333] to 59612 [95% CI 31854-94689] DALY per year, corresponding to 3.54 to 3.56 DALY per 1000 population. Average yearly incidence rates per 10 000 person-years were 0.23 [95% CI 0.21-0.26] for NCC, 4.89 [95% CI 4.78-5.00] for epilepsy, 0.130 [95% CI 0.11-0.15] for status epilepticus, 0.62 [95% CI 0.58-0.66] for migraine headache, and 1.02 [95% CI 0.98-1.07] for hydrocephalus. Most important significant spatial clusters (p<0.0001) were located in the southern region of the highlands of the country.Conclusion/significanceThis is the first study in South America to calculate estimates for burden of NCC and one of the few using spatial analysis to show the importance of sequelae other than epilepsy that play an important role in the impact of human neurocysticercosis.

Project description:Neurocysticercosis (NCC) caused by Taenia solium is a serious neurological disease. In humans neurological symptoms have been thoroughly studied and documented, however, there is limited information on clinical signs in pigs infected with T. solium cysticerci. Among the scientific community, it is in fact believed that pigs with NCC rarely show neurological signs. The aim of this study was to describe clinical manifestations associated with NCC in pigs and correlate the manifestations to the number and distribution of cysticerci in brains of naturally infected pigs in Tanzania. Sixteen infected and 15 non-infected control pigs were observed for 14 days during daylight hours, and subsequently videotaped for another 14 consecutive days using close circuit television cameras. All occurrences of abnormal behaviour (trembling, twitching, mouth and ear paralysis, ataxia, dribbling, salivating, eye blinking, walking in circles) were recorded. At the end of the recording period, pigs were slaughtered and their brains dissected, cysticerci counted and locations noted. During the recording period, two infected pigs were observed having seizures. Some of the observed autonomic signs during a seizure were chewing motions with foamy salivation and ear stiffening. Motor signs included tonic muscle contractions followed by a sudden diminution in all muscle function leading to collapse of the animal. Stereotypic walking in circles was observed on several occasions. At dissection, both pigs had a high number of brain cysticerci (241 and 247 cysticerci). The two pigs with seizures were also older (36 months) compared to the others (18.3 months, ± 8.2 standard deviation). Results of this study have shown that pigs with NCC can develop clinical signs and suffer from seizures like humans with symptomatic NCC. Results of this study could potentially open up a new experimental pathway to explore the aetiology of neurological symptoms in humans with NCC associated epilepsy.

Dataset Information

Spatial distribution of Taenia solium exposure in humans and pigs in the Central Highlands of Vietnam.

Background

Methodology/principal findings

Conclusions

Publications

Spatial distribution of Taenia solium exposure in humans and pigs in the Central Highlands of Vietnam.

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