Wildlife Trade and Human Health in Lao PDR: An Assessment of the Zoonotic Disease Risk in Markets

Abstract

Although the majority of emerging infectious diseases can be linked to wildlife sources, most pathogen spillover events to people could likely be avoided if transmission was better understood and practices adjusted to mitigate risk. Wildlife trade can facilitate zoonotic disease transmission and represents a threat to human health and economies in Asia, highlighted by the 2003 SARS coronavirus outbreak, where a Chinese wildlife market facilitated pathogen transmission. Additionally, wildlife trade poses a serious threat to biodiversity. Therefore, the combined impacts of Asian wildlife trade, sometimes termed bush meat trade, on public health and biodiversity need assessing. From 2010 to 2013, observational data were collected in Lao PDR from markets selling wildlife, including information on volume, form, species and price of wildlife; market biosafety and visitor origin. The potential for traded wildlife to host zoonotic diseases that pose a serious threat to human health was then evaluated at seven markets identified as having high volumes of trade. At the seven markets, during 21 observational surveys, 1,937 alive or fresh dead mammals (approximately 1,009 kg) were observed for sale, including mammals from 12 taxonomic families previously documented to be capable of hosting 36 zoonotic pathogens. In these seven markets, the combination of high wildlife volumes, high risk taxa for zoonoses and poor biosafety increases the potential for pathogen presence and transmission. To examine the potential conservation impact of trade in markets, we assessed the status of 33,752 animals observed during 375 visits to 93 markets, under the Lao PDR Wildlife and Aquatic Law. We observed 6,452 animals listed by Lao PDR as near extinct or threatened with extinction. The combined risks of wildlife trade in Lao PDR to human health and biodiversity highlight the need for a multi-sector approach to effectively protect public health, economic interests and biodiversity.

Fig 1. Locations in Lao PDR where basic observational wildlife trade surveys were undertaken between 2010 and 2013.

(Created with QGIS v2.6.1-Brighton software and map data from OpenStreetMap contributors).

Fig 2. Average number of alive or fresh dead animals per day for markets A-G.

Mammals (Mammalia), wild birds (Aves) and reptiles (Reptilia) are shown. The seven high volume markets are listed and Lao PDR province for each corresponding market are provided.

Fig 3. Number of potential significant zoonoses per mammalian family based on total live and fresh dead mass (A) and individual animal count (B) of mammals.

Individual animal count and biomass (kg) observed for seven markets over 21 visits on a log scale are shown. Only families capable of hosting one or more zoonosis are represented. Precise biomass and counts are provided in the S1 Table.

Fig 4. Comparison of average price of fresh dead wildlife (February–April 2012) to the price of domestic pork in Lao PDR.

Bars represent standard deviation. Where wildlife was priced per individual, price was converted to Kip/kg using average body weight for wildlife species. The average price was based on observations of sales of: nine common palm civet, 33 Pallas’s squirrel, 14 Indian giant flying squirrel, 17 Pteropodidae, 40 Muridae and six domestic pork samples. For sales observations of the brush-tailed porcupine (n = 10), muntjac (n = 10) and wild boar (n = 3), wildlife was priced per kilogram. The price of rice (used as an indicator for the expected level of price variation across the country) did not vary significantly between vendors in markets or between different markets; the average across all markets was 4,982 Kip/kg.