A systematic review of taeniasis, cysticercosis and trichinellosis in Vietnam

Abstract

Taeniasis, cysticercosis and trichinellosis have been ranked as the most important food-borne parasites of humans in terms of public health, socioeconomic and trade impact. Despite this, information on these food-borne zoonoses in Vietnam is scarce and fragmented, and many local reports remain inaccessible to the international research community. This study aims to conduct comprehensive literature searches to report on the incidence and estimate the true prevalence of taeniasis in humans and T. solium cysticercosis in humans and pigs in Vietnam utilizing Bayesian models; in addition, to report the incidence and the distribution of trichinellosis. A Bayesian approach was used to estimate the true prevalence of taeniasis and cysticercosis based on published diagnostic test characteristics used in each published cross-sectional survey. The utilization of coproscopic-based examination of Taenia eggs in stool, although highly specific for genus-level detection, has poor sensitivity and led to an underestimation of the prevalence of human taeniasis. Similarly, post-mortem-based surveys of T. solium cysticercosis in pigs also led to the underestimation of prevalence of porcine cysticercosis. On the other hand, the low specificity of immunodiagnostic methods, in particular Ab-ELISA, led to a likely overestimation of T. solium cysticercosis in humans. Due to the use of imperfect diagnosis tests combined with poor descriptions of sampling methods, our ability to draw solid conclusions from these data is limited. We estimate that the true prevalence of taeniasis and T. solium cysticercosis in rural ‘hotspots’, is as high as 13% for each, in humans. Taeniasis and T. solium cysticercosis occurs in 60 of the 63 provinces of Vietnam. Most of the information relating to the distribution and prevalence of porcine cysticercosis is limited to commercial abattoir surveys. In Vietnam, Taenia asiatica appears to be confined to the north where it occurs sympatrically with T. solium and Taenia saginata. The status of T. asiatica in Central and South Vietnam remains unascertained. To date, five outbreaks of trichinellosis have been reported in the north and northwest of Vietnam, affecting a total of 114 people and responsible for eight fatalities. In the same region, studies of free-roaming pigs showed evidence of high levels of exposure to Trichinella and, in cases where larvae were recovered, the species present were identified as Trichinella spiralis. Based on five studies, the main risk factors for pork-borne zoonoses in Vietnam include the consumption of undercooked/raw meat and vegetables and the use of night-soil for fertilization of local produce. This systematic review draws attention to the importance of these pork-borne zoonoses.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-017-2085-9) contains supplementary material, which is available to authorized users.

Epidemiology of taeniosis, cysticercosis and trichinellosis in Iran: A systematic review

“…Of the 37 articles reviewed in the current study, no single case of T. solium taeniosis was reported among humans in Iran. On the contrary, relatively higher infection rates have been reported in other areas across the world such as Vietnam, where up to 13% of the people in rural hotspots were reportedly infected with T. solium (Ng‐Nguyen et al, ). Given that T. solium taeniosis is transmitted to humans through consumption of pork, Islamic dietary laws which strictly forbid pork consumption among Muslims could have been responsible for the absence of T. solium taeniosis among humans in Iran.…”

“…Taeniosis, cysticercosis and trichinellosis are well‐known foodborne parasitic diseases of humans with significant public health and economic importance (Ng‐Nguyen, Stevenson, & Traub, ), yet little is known about the prevalence of these foodborne zoonoses in Iran. Indeed, in Iran, being one of the biggest Muslim countries in the world, consumption of pork and meat from carrion is prohibited for religious reasons, while hunting of wild boar is merely authorized for the ethnic Armenians, Jews and Zoroastrians in the country.…”

“…cysticercosis prevalence rates reported in Iran are relatively low compared to those reported in countries like Vietnam where Taenia spp. cysticercosis occurs in over 50 of the 63 provinces of the country (Ng‐Nguyen et al, ).…”

Habit of cooking pork on hot stones as main risk of cysticercosis

“…(5) A study on the risk factors of taeniasis/ cysticercosis in Vietnam reported that consuming undercooked or raw pork, raw vegetables or salads, and unboiled water are important positive factors for the spread of the disease, whereas hand washing with soap before meals and after defecation is important in its prevention. (10) The risk factors of taeniasis/cysticercosis transmission in Africa, Asia, Latin America, and Southeast Asia are generally similar, i.e. community culture, poor environmental sanitation, low level of personal hygiene, low educational level, free-roaming pigs, consumption of undercooked or raw pork, and consumption of raw vegetables or salads.…”

“…community culture, poor environmental sanitation, low level of personal hygiene, low educational level, free-roaming pigs, consumption of undercooked or raw pork, and consumption of raw vegetables or salads. (5,10) Similarly, the risk factors of taeniasis/cysticercosis transmission in Papua are associated with the consumption of undercooked pork and vegetables, low educational level on hygiene, and free-roaming pigs. (11) However, there is a need for further study on the management of pork consumption.…”