Véronique Chevalier

Absence of Middle East Respiratory Syndrome Coronavirus in Camelids, Kazakhstan, 2015.

To the Editor: Middle East respiratory syndrome coronavirus (MERS-CoV) acquired from animals causes severe pneumonia in humans, with some chains of human-to-human transmission, leading to large outbreaks. MERS-CoV is a cause of concern for global public health. The only natural host of MERS-CoV identified so far is the dromedary camel (Camel dromedarius) (1,2), and transmission from camels to humans has been documented (3). The geographic distribution of MERS-CoV in dromedaries extends beyond the Arabian Peninsula (where human cases have been reported) to North and East Africa (where human cases have not been reported) (2,4). However, MERS-CoV from a camel in Egypt and MERS-CoV from a human were phenotypically similar in tropism and replication competence in ex vivo cultures of the human respiratory tract (5). n nOur previous study demonstrated no evidence of MERS-CoV infection in Bactrian camels in Mongolia (6). The question whether MERS-CoV is endemic in camelids in Central Asia remains unanswered. MERS-CoV RNA was detected in swab samples from camels in Iran, which had been imported from Pakistan; however, where the infection was acquired is unclear (7). n nIn Asia, Kazakhstan is of particular interest because large populations of 2 major camelid species overlap: 90% Bactrian (Kazakh breed including 3 ecotypes) and ≈10% dromedary (Arvana breed from Turkmenistan) and their hybrids (8). To determine whether MERS-CoV is present in camelids in Kazakhstan, we conducted a seroepidemiologic survey. n nDuring February–March 2015, blood was collected from 550 female camels (455 dromedary, 95 Bactrian) (Figure) in 2 regions, Almaty and Shymkent, which differ in camelid density (0.034 and 0.20 camels/km2, respectively; http://www.stat.gov.kz). Dromedaries were sampled in the cities/villages of Kyzylorda (105 animals from 2 herds), Zanakorgan (35 animals from 1 herd), Sholakkorgan (110 animals from 2 herds), and Akshiy (205 animals from 4 herds). Bactrian camels were sampled in Sholakkorgan (40 animals from 1 herd) and Kanshengel (55 animals from 1 herd) (Figure). For dromedary camels, mean age was 6.1 years (SD 3–7 years) and mean herd size was 53.6 animals (SD 31–70); for Bactrian camels, mean age was 6.5 years (SD 5–8 years) and mean herd size was 48.6 animals (SD 40–55). Serum samples were tested for MERS-CoV antibodies at a screening dilution of 1:20 by using a validated MERS-CoV (strain EMC) spike pseudoparticle neutralization test (9). Positive and negative controls were included in each run. Absence of positivity for any sample indicated a lack of recent or past MERS-CoV infection. n n n nFigure n nDensity of camelids in Kazakhstan (extracted from the Ministry of National Economy of the Republic of Kazakhstan Committee on Statistics, Department of Statistics; http://www.stat.gov.kz) and specimen collection for detection of Middle East respiratory ... n n n nTwo randomly selected samples each from dromedaries from Kyzlorda, Zanakorgan, and Akshiy and Bactrians from Sholakkorgan and Kanshenegel were tested for neutralizing antibody to bovine coronavirus (9). All 10 samples were seropositive, as has been reported for Bactrian camels in Mongolia and the Middle East (6,9). n nGiven the uniformly high seroprevalence of MERS-CoV infection among dromedaries in Africa and the Arabian Peninsula, the lack of infection in dromedaries in southern Kazakhstan was surprising. Because genetically diverse MERS-CoV from Africa remains antigenically conserved with viruses from the Arabian Peninsula, the lack of antibodies is probably not explained by antigenically divergent strains (9). Feral dromedaries in Australia, which originated from animals imported from Afghanistan or Pakistan during 1840–1907, are also seronegative for MERS-CoV (10). In contrast, bovine-like coronavirus seems to be present in dromedaries everywhere (including Kazakhstan and Australia). n nOur study was limited by sample size and by geographic coverage. Of the ≈180,000 camels in Kazakhstan, we studied camelids from only 2 of the 13 provinces. No samples were collected from the western part of the country near Turkmenistan, where dromedaries are also common. n nDromedaries are clearly a natural host of MERS-CoV. However, the finding that MERS-CoV is not endemic in dromedaries in all geographic regions suggests the possibility that dromedaries may not be the ultimate natural reservoir (i.e., the long-term host of a pathogen of an infectious disease). Topography (i.e., mountain chains) may limit camel movements from the Middle East or Africa to Central Asia, although such interchange certainly occurred centuries ago as a consequence of the silk-trade routes through southern Kazakhstan. The only known recent imports to Kazakhstan are dromedaries (Arvana breed), brought from Turkmenistan for cross-breeding with Bactrians to improve milk production (8). The findings that MERS-CoV is not universally endemic in dromedaries raises the hypothesis that certain species of bats or some other animal, the environment, or both, may constitute a maintenance community and be the true natural reservoir of MERS-CoV and that the virus spills over to camels and is maintained within camels for varying periods of time. Further studies on the epidemiology of MERS-CoV infection among camelids from central Asia are warranted.

How to reach the poor? Surveillance in low-income countries, lessons from experiences in Cambodia and Madagascar.

Surveillance of animal diseases in developing countries faces many constraints. Innovative tools and methods to enhance surveillance in remote and neglected areas should be defined, assessed and applied in close connection with local farmers, national stakeholders and international agencies. The authors performed a narrative synthesis of their own publications about surveillance in Madagascar and Cambodia. They analysed the data in light of their fieldwork experiences in the two countries very challenging environments. The burden of animal and zoonotic diseases (e.g. avian influenza, African swine fever, Newcastle disease, Rift Valley fever) is huge in both countries which are among the poorest in the world. Being poor countries implies a lack of human and financial means to ensure effective surveillance of emerging and endemic diseases. Several recent projects have shown that new approaches can be proposed and tested in the field. Several advanced participatory approaches are promising and could be part of an innovative method for improving the dialogue among different actors in a surveillance system. Thus, participatory modelling, developed for natural resources management involving local stakeholders, could be applied to health management, including surveillance. Data transmission could benefit from the large mobile-phone coverage in these countries. Ecological studies and advances in the field of livestock surveillance should guide methods for enhancing wildlife monitoring and surveillance. Under the umbrella of the One Health paradigm, and in the framework of a risk-based surveillance concept, a combination of participatory methods and modern technologies could help to overcome the constraints present in low-income countries. These unconventional approaches should be merged in order to optimise surveillance of emerging and endemic diseases in challenging environments.

Intensive Circulation of Japanese Encephalitis Virus in Peri-urban Sentinel Pigs near Phnom Penh, Cambodia.

Despite the increased use of vaccination in several Asian countries, Japanese Encephalitis (JE) remains the most important cause of viral encephalitis in Asia in humans with an estimated 68,000 cases annually. Considered a rural disease occurring mainly in paddy-field dominated landscapes where pigs are amplifying hosts, JE may nevertheless circulate in a wider range of environment given the diversity of its potential hosts and vectors. The main objective of this study was to assess the intensity of JE transmission to pigs in a peri-urban environment in the outskirt of Phnom Penh, Cambodia. We estimated the force of JE infection in two cohorts of 15 sentinel pigs by fitting a generalised linear model on seroprevalence monitoring data observed during two four-month periods in 2014. Our results provide evidence for intensive circulation of JE virus in a periurban area near Phnom Penh, the capital and most populated city of Cambodia. Understanding JE virus transmission in different environments is important for planning JE virus control in the long term and is also an interesting model to study the complexity of vector-borne diseases. Collecting quantitative data such as the force of infection will help calibrate epidemiological model that can be used to better understand complex vector-borne disease epidemiological cycles.

Risk factors for MERS coronavirus infection in dromedary camels in Burkina Faso, Ethiopia, and Morocco, 2015

Understanding Middle East respiratory syndrome coronavirus (MERS-CoV) transmission in dromedary camels is important, as they consitute a source of zoonotic infection to humans. To identify risk factors for MERS-CoV infection in camels bred in diverse conditions in Burkina Faso, Ethiopia and Morocco, blood samples and nasal swabs were sampled in February–March 2015. A relatively high MERS-CoV RNA rate was detected in Ethiopia (up to 15.7%; 95% confidence interval (CI): 8.2–28.0), followed by Burkina Faso (up to 12.2%; 95% CI: 7–20.4) and Morocco (up to 7.6%; 95% CI: 1.9–26.1). The RNA detection rate was higher in camels bred for milk or meat than in camels for transport (p = 0.01) as well as in younger camels (p = 0.06). High seropositivity rates (up to 100%; 95% CI: 100–100 and 99.4%; 95% CI: 95.4–99.9) were found in Morocco and Ethiopia, followed by Burkina Faso (up to 84.6%; 95% CI: 77.2–89.9). Seropositivity rates were higher in large/medium herds (≥51 camels) than small herds (p = 0.061), in camels raised for meat or milk than for transport (p = 0.01), and in nomadic or sedentary herds than in herds with a mix of these lifestyles (p < 0.005).

Development and assessment of a geographic knowledge-based model for mapping suitable areas for Rift Valley fever transmission in Eastern Africa

Rift Valley fever (RVF), a mosquito-borne disease affecting ruminants and humans, is one of the most important viral zoonoses in Africa. The objective of the present study was to develop a geographic knowledge-based method to map the areas suitable for RVF amplification and RVF spread in four East African countries, namely, Kenya, Tanzania, Uganda and Ethiopia, and to assess the predictive accuracy of the model using livestock outbreak data from Kenya and Tanzania. Risk factors and their relative importance regarding RVF amplification and spread were identified from a literature review. A numerical weight was calculated for each risk factor using an analytical hierarchy process. The corresponding geographic data were collected, standardized and combined based on a weighted linear combination to produce maps of the suitability for RVF transmission. The accuracy of the resulting maps was assessed using RVF outbreak locations in livestock reported in Kenya and Tanzania between 1998 and 2012 and the ROC curve analysis. Our results confirmed the capacity of the geographic information system-based multi-criteria evaluation method to synthesize available scientific knowledge and to accurately map (AUC = 0.786; 95% CI [0.730–0.842]) the spatial heterogeneity of RVF suitability in East Africa. This approach provides users with a straightforward and easy update of the maps according to data availability or the further development of scientific knowledge.

One Health and EcoHealth: the same wine in different bottles?

-- (Published: 17 February 2016) Citation: Infection Ecology and Epidemiology 2016, 6: 30978 - http://dx.doi.org/10.3402/iee.v6.30978

MERS-CoV in Arabian camels in Africa and Central Asia

Middle East Respiratory Syndrome Coronavirus (MERS-CoV) causing infections in humans is genetically indistinguishable from the virus found in Arabian camels (dromedaries) in the Middle East. Although no primary human case of MERS was reported outside the Arabian Peninsula, camel populations in Africa are known to have high prevalence of antibodies against MERS-CoV. We carried out surveillance for MERS-CoV in dromedaries in Africa and Central Asia. By MERS-CoV spike pseudoparticle neutralization assay we confirmed that camel serum samples from African countries have high prevalence of MERS-CoV antibodies. Using RT-qPCR we detected MERS-CoV positives in camel nasal swabs from all different African countries from which samples were collected. However, dromedary serum and swab samples from Kazakhstan in Central Asia were negative for MERS-CoV by these assays. Phylogenetic analysis of the spike gene revealed that MERS-CoVs from Africa formed a cluster closely related to but distinct from the viruses from the Arabian Peninsula. Results from this study suggest that MERS-CoV is actively circulating in dromedary populations in Africa and the virus in Africa is phylogenetically distinct from that in the Middle East. (Resume dauteur)

Climate Change and Vector-Borne Diseases

Diseases transmitted by insect vectors have a major impact on human and animal health, as well as on the economy of societies. Because of their modes of transmission, these vector-borne diseases—zoonotic or not—are particularly sensitive to climate change. The climate and its variations determine, sometimes substantially, the presence of vectors at a given place, as well as their density and capacity to transmit diseases. The climate also has an influence on the presence and density of animals and humans, in addition to the survival capacities of pathogens in a given environment. All of the components, conditions and processes necessary for the transmission of these diseases form a complex dynamic system whose behaviour, under the influence of the climate and other environmental variables, will determine whether or not transmission will occur. Experimental and epidemiological studies are carried out in laboratory and field conditions to gain greater insight into the underlying biological processes and measure the impact of climate parameters on these processes. Mathematical modelling is used to represent these systems and simulate their behaviour under different environmental conditions. This major tool sheds light on the biological phenomena involved in the transmission of given pathogens, while also simulating, over a more or less long time scale, spatiotemporal variations in the intensity of this transmission so as to be able to tailor control strategies against these diseases.

Modelling and assessment of combining gilt vaccination, vector control and pig herd management to control Japanese Encephalitis virus transmission in Southeast Asia

Despite existence of human vaccines, Japanese Encephalitis (JE) remains a prominent public health problem in Southeast Asia (SEA). JE is caused by a Flavivirus which is transmitted between pigs, the main amplifying hosts, by Culex mosquito bites. Therefore, sow vaccination, pig herd management and vector control –or a combination of these three potential control measures, might constitute additional control measures contributing to reduce JE health impact in humans, and economic losses in pig farms. We built a deterministic metapopulation model, combining a pig and a Culex mosquito vector population, to represent JE virus (JEV) transmission dynamic within a pig herd. The dynamic of the epidemiological systems resulted from an infectious process, operating in continuous time, combined with the pig breeding process that was modeled based on discrete events occurring instantaneously. We used this model to simulate JEV transmission within a continuum of plausible pig breeding systems encountered in SEA, ranging from backyards to semi-commercial systems. We then analyzed the joint effects of the three tested control measures, namely sow vaccination, pig herd management and vector control, on several indicators characterizing (i) the ability of different pig breeding systems to be simultaneously profitable and allow JEV eradication in the herd, (ii) the impact of JE on pig production and the profitability of gilt vaccination, and (iii) the risk for human beings living in the vicinity of pig herds and/or near pig slaughterhouses. According to our model, herd management has no effect on JEV circulation. Vector control alone is a major control tool but shows paradoxical effects that should be considered in any mosquito based control strategy. Combining sow vaccination and vector control could be an alternative or an additional measure to human vaccination to efficiently reduce both JE incidence in humans and the economic impact of JE infection on pig farms. Author summary Japanese Encephalitis (JE) still has an important impact on human health in Southeast Asia. Human vaccination is an efficient tool to protect humans but it may not be effective against emerging strains, and poor or remote population may not be able to afford it. Severe outbreaks still occur. JE virus (JEV) is primarily transmitted between pigs and mosquitoes. When infected after sexual maturity, pigs show reproduction disorders leading to economic losses. We propose a modelling approach to investigate the joint effect of three additional control measures, namely sow vaccination, vector control, and pig herd management on JEV transmission dynamic, risk for humans and pigs, and pig breeding sustainability. According to our results, vector control, associated or not with sow vaccination, may be an efficient tool to reduce JE incidence in both human and pigs.

How much does direct transmission between pigs contribute to Japanese Encephalitis virus circulation? A modelling approach in Cambodia

Japanese Encephalitis (JE) is the most important cause of human encephalitis throughout Asia and the Pacific. Although JE is a vector-borne disease, it has been demonstrated experimentally that transmission between pigs can occur through direct contact. Whether pig-to-pig transmission plays a role in the natural epidemiological cycle of JE remains unknown. To assess whether direct transmission between pigs may occur under field conditions, we built two mathematical models of JE transmission incorporating vector-borne transmission alone or a combination of vector-borne and direct transmission. We used Markov Chain Monte Carlo (MCMC) techniques to estimate the parameters of the models. We fitted the models to (i) two serological datasets collected longitudinally from two pig cohorts (C1 and C2) during two periods of four months on a farm on the outskirts of Phnom-Penh, Cambodia and to (ii) a cross-sectional (CS) serological survey dataset collected from 505 swine coming from eight different provinces of Cambodia. In both cases, the model incorporating both vector-borne and direct transmission better explained the data. We computed the value of the basic reproduction number R0 (2.93 for C1, 2.66 for C2 and 2.27 for CS), as well as the vector-borne reproduction number Rpv and the direct transmission reproduction number Rpp. We then determined the contribution of direct transmission on R0 (11.90% for C1, 11.62% for C2 and 7.51% for CS). According to our results, the existence of pig-to-pig transmission is consistent with our swine serological data. Thus, direct transmission may contribute to the epidemiological cycle of JE in Cambodia. These results need to be confirmed in other eco-climatic settings, in particular in temperate areas where pig-to-pig transmission may facilitate the persistence of JE virus (JEV) during cold seasons when there are no or few mosquitoes.