Rodents and Risk in the Mekong Delta of Vietnam: Seroprevalence of Selected Zoonotic Viruses in Rodents and Humans

Abstract

In the Mekong Delta in southern Vietnam, rats are commonly traded in wet markets and sold live for food consumption. We investigated seroprevalence to selected groups of rodent-borne viruses among human populations with high levels of animal exposure and among co-located rodent populations. The indirect fluorescence antibody test (IFAT) was used to determine seropositivity to representative reference strains of hantaviruses (Dobrava virus [DOBV], Seoul virus [SEOV]), cowpox virus, arenaviruses (lymphocytic choriomeningitis virus [LCMV]), flaviviruses (tick-borne encephalitis virus [TBEV]), and rodent parechoviruses (Ljungan virus), using sera from 245 humans living in Dong Thap Province and 275 rodents representing the five common rodent species sold in wet markets and present in peridomestic and farm settings. Combined seropositivity to DOBV and SEOV among the rodents and humans was 6.9% (19/275) and 3.7% (9/245), respectively; 1.1% (3/275) and 4.5% (11/245) to cowpox virus; 5.4% (15/275) and 47.3% (116/245) for TBEV; and exposure to Ljungan virus was 18.8% (46/245) in humans, but 0% in rodents. Very little seroreactivity was observed to LCMV in either rodents (1/275, 0.4%) or humans (2/245, 0.8%). Molecular screening of rodent liver tissues using consensus primers for flaviviruses did not yield any amplicons, whereas molecular screening of rodent lung tissues for hantavirus yielded one hantavirus sequence (SEOV). In summary, these results indicate low to moderate levels of endemic hantavirus circulation, possible circulation of a flavivirus in rodent reservoirs, and the first available data on human exposures to parechoviruses in Vietnam. Although the current evidence suggests only limited exposure of humans to known rodent-borne diseases, further research is warranted to assess public health implications of the rodent trade.

Detection of potentially novel paramyxovirus and coronavirus viral RNA in bats and rats in the Mekong Delta region of southern Viet Nam

“…The rodent surveys and sampling were conducted as previously described by Van Cuong et al. (). Briefly, rats were purchased from three markets in Dong Thap Province in the Mekong Delta (two rat markets in Cao Lanh City and one market in Tam Nong District) every 4 months for 2 years, between 2012 and 2014.…”

“…Bats are common in Viet Nam and may pose a threat from the circulation of zoonotic RNA viruses. Further, in parts of the country, rats are commonly trapped in the rice fields and sold live for consumption; 3,300–3,600 tonnes are sold nationally annually (Van Cuong et al., ). Rats and other rodents are also recognized as a reservoir of zoonotic viruses that can be transmitted via close contact with saliva, urine or faeces; the circulation of hantavirus has been reported in rats in Viet Nam (Van Cuong et al., ).…”

“…Further, in parts of the country, rats are commonly trapped in the rice fields and sold live for consumption; 3,300–3,600 tonnes are sold nationally annually (Van Cuong et al., ). Rats and other rodents are also recognized as a reservoir of zoonotic viruses that can be transmitted via close contact with saliva, urine or faeces; the circulation of hantavirus has been reported in rats in Viet Nam (Van Cuong et al., ). As South‐East Asia is a hot spot for zoonotic viruses, the WT‐VIZIONS (Wellcome Trust‐Vietnamese Initiative on Zoonotic Infections) project (Rabaa et al., ) is aiming to generate data on the circulation of viral zoonotic pathogens that pose a risk to human health.…”

Hantavirus infection: a global zoonotic challenge

“…SEOV has also been detected in rodents from Indonesia (Ibrahim et al, 1996). In the Mekong Delta of Vietnam, rodents can be infected with DOBV and SEOV with a positive rate of 6.9% (Van Cuong et al, 2015). There have also been studies claiming that selenium deficiency is correlated with increased prevalence of hantavirus infections in both humans and rodents (Fang LQ et al, 2015).…”

Japanese encephalitis circulation pattern in swine of northern Vietnam and consequences for swine's vaccination recommendations

“…Using DD as an explanatory variable, we were able to build a simple model taking into account JE transmission seasonality in northern Vietnam and to predict the average age of pigs at infection depending on their month of birth. Our data set relied on ELISA‐tested serum samples, and Vietnam is an area where several flaviviruses are co‐circulating (such as Dengue virus (Phuong et al., ) and probably others (Van Cuong et al., )). To make sure our model is indeed a model of JE circulation, we had to confirm our ELISA‐positive samples with VNT as ELISA is highly sensitive but lacks specificity.…”