Urban livestock-keeping and dengue in urban and peri-urban Hanoi, Vietnam

Associations between livestock keeping, morbidity and nutritional status of children and women in low- and middle-income countries: a systematic review

Livestock keeping can positively influence the nutritional status of populations and households through increased consumption of animal-source foods (ASF) and other indirect pathways, but can also adversely affect health by increasing the risk of diseases. We conducted a systematic review synthesising the current state of knowledge on the associations among livestock keeping, infectious disease and the nutritional status of children under 5 years and women of reproductive age in low- and lower-middle-income countries (LMICs). A comprehensive search of 12 electronic databases and grey literature sources published from 1991 to the end of December 2020 was conducted. Investigations exploring relationships between livestock keeping and risk of infectious disease transmission and nutritional status were selected using pre-defined inclusion criteria. After screening and filtering of 34,402 unique references, 176 references were included in the final synthesis. Most (160/176, 90.1%) of the references included in the final synthesis were from sub-Saharan Africa (SSA) and Asia. About two out of every five (42%) studies reviewed showed that livestock production is associated with improved height-for-age Z scores (HAZ) and weight-for-length/height Z scores (WHZ), while close to a third (30.7%) with improved weight-for-age Z scores (WAZ). Similarly, livestock production showed a positive or neutral relationship with women's nutritional status in almost all the references that reported on the topic. Conversely, four-fifths (66/81, 79.5%) of the references reporting on infection and morbidity outcomes indicated that livestock keeping is linked to a wide range of infectious disease outcomes, which are spread primarily through water, food and insects. In conclusion, in many LMIC settings, livestock production is associated with better nutritional outcomes but also a higher risk of disease transmission or morbidity among women and children.This review was prospectively registered on PROSPERO 2020 [CRD42020193622].

Survey of mosquito species and mosquito-borne viruses in residential areas along the Sino-Vietnam border in Yunnan Province in China

Mosquitoes are capable of carrying complex pathogens, and their feeding habits on the mammalian blood can easily mediate the spread of viruses. Surveillance of mosquito-based arbovirus enables the early prevention and control of mosquito-borne arboviral diseases. The climate and geography of Yunnan Province in China are ideal for mosquitoes. Yunnan shares borders with several other countries; therefore, there exists a high risk of international transmission of mosquito-mediated infectious diseases. Previous studies have focused more on the Sino-Laos and Sino-Myanmar borders. Therefore, we focused on the neighborhoods of Malipo and Funing counties in Wenshan Prefecture, Yunnan Province, China, which are located along the Sino-Vietnam border, to investigate the species of mosquitoes and mosquito-borne viruses in the residential areas of this region. This study collected 10,800 mosquitoes from 29 species of 8 genera and grouped to isolate mosquito-borne viruses. In total, 62 isolates were isolated and classified into 11 viral categories. We demonstrated a new distribution of mosquito-borne viruses among mosquitoes in border areas, including Tembusu and Getah viruses, which can cause animal outbreaks. In addition, Dak Nong and Sarawak viruses originating from Vietnam and Malaysia, respectively, were identified for the first time in China, highlighting the complexity of mosquito-borne viruses in the Sino-Vietnam border region. The awareness of the importance of viral surveillance and prevention measures in border areas should be further encouraged to prevent future outbreaks of potentially infectious diseases.

The Distribution and Composition of Vector Abundance in Hanoi City, Vietnam: Association with Livestock Keeping and Flavivirus Detection

BACKGROUND

Dengue virus and Japanese encephalitis virus are two common flaviviruses that are spread widely by Aedes and Culex mosquitoes. Livestock keeping is vital for cities; however, it can pose the risk of increasing the mosquito population. Our study explored how livestock keeping in and around a large city is associated with the presence of mosquitoes and the risk of them spreading flaviviruses.

METHODS

An entomological study was conducted in 6 districts with 233 households with livestock, and 280 households without livestock, in Hanoi city. BG-Sentinel traps and CDC light traps were used to collect mosquitoes close to animal farms and human habitats. Adult mosquitoes were counted, identified to species level, and grouped into 385 pools, which were screened for flaviviruses using a pan-flavivirus qPCR protocol and sequencing.

RESULTS

A total of 12,861 adult mosquitoes were collected at the 513 households, with 5 different genera collected, of which the Culex genus was the most abundant. Our study found that there was a positive association between livestock keeping and the size of the mosquito population-most predominantly between pig rearing and Culex species (p < 0.001). One pool of Cx. tritaeniorhynchus, collected in a peri-urban district, was found to be positive for Japanese encephalitis virus.

CONCLUSIONS

The risk of flavivirus transmission in urban areas of Hanoi city due to the spread of Culex and Aedes mosquitoes could be facilitated by livestock keeping.

Spatial distribution of Culex mosquito abundance and associated risk factors in Hanoi, Vietnam

Japanese encephalitis (JE) is the major cause of viral encephalitis (VE) in most Asian-Pacific countries. In Vietnam, there is no nationwide surveillance system for JE due to lack of medical facilities and diagnoses. Culex tritaeniorhynchus, Culex vishnui, and Culex quinquefasciatus have been identified as the major JE vectors in Vietnam. The main objective of this study was to forecast a risk map of Culex mosquitoes in Hanoi, which is one of the most densely populated cities in Vietnam. A total of 10,775 female adult Culex mosquitoes were collected from 513 trapping locations. We collected temperature and precipitation information during the study period and its preceding month. In addition, the other predictor variables (e.g., normalized difference vegetation index [NDVI], land use/land cover and human population density), were collected for our analysis. The final model selected for estimating the Culex mosquito abundance included centered rainfall, quadratic term rainfall, rice cover ratio, forest cover ratio, and human population density variables. The estimated spatial distribution of Culex mosquito abundance ranged from 0 to more than 150 mosquitoes per 900m2. Our model estimated that 87% of the Hanoi area had an abundance of mosquitoes from 0 to 50, whereas approximately 1.2% of the area showed more than 100 mosquitoes, which was mostly in the rural/peri-urban districts. Our findings provide better insight into understanding the spatial distribution of Culex mosquitoes and its associated environmental risk factors. Such information can assist local clinicians and public health policymakers to identify potential areas of risk for JE virus. Risk maps can be an efficient way of raising public awareness about the virus and further preventive measures need to be considered in order to prevent outbreaks and onwards transmission of JE virus.

Risk factors of dengue fever in an urban area in Vietnam: a case-control study

Background

Dengue is a mosquito-borne flavivirus present in many metropolitan cities of tropical countries.

Methods

During and after the dengue season (September 2018 to January 2019), we conducted a case-control study in order to determine the risk factors for dengue fever in Hanoi city, Vietnam. 98 dengue patients and 99 patients with other acute infections, such as Hepatitis B virus infection, were recruited at Department of Infectious Disease of Bach Mai national hospital in Hanoi. Patients were interviewed using a structured questionnaire covering demographic, housing, environmental factors and knowledge, attitude, and practice on dengue prevention and control. Univariate analysis and multivariable logistic regression were used to determine the risk factors of dengue status.

Results

The mean score of knowledge items and practice items was only 7.9 out of total 19 points and 3.9 out of total 17 points, respectively. While the mean score of attitude items was 4.8 out of total 6 points. Multivariable logistic regression indicated that older patients had lesser risk of getting dengue infection as compared to younger adults aged 16–30, and patients living in peri-urban districts were less likely to suffer of dengue fever than patients living in central urban districts (OR = 0.31; 95% CI 0.13–0.75). This study could not find any association with occupation, water storage habit, knowledge, attitude, or practice on dengue prevention.

Conclusions

All patients had a relatively low level of knowledge and practice on dengue prevention and control. However, the attitude of the participants was good. We found that age group and living district were the risk factors correlated with the dengue status. Communication programs on raising dengue awareness should be repeated all year round and target particular groups of adolescents, younger adults, landlords and migrants from other provinces to improve their knowledge and encourage them to implement preventive measures against dengue fever.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-021-10687-y.

Dogs as Sentinels for Flavivirus Exposure in Urban, Peri-Urban and Rural Hanoi, Vietnam

Diseases caused by flaviviruses, including dengue fever and Japanese encephalitis, are major health problems in Vietnam. This cross-sectional study explored the feasibility of domestic dogs as sentinels to better understand risks of mosquito-borne diseases in Hanoi city. A total of 475 dogs serum samples from 221 households in six districts of Hanoi were analyzed by a competitive enzyme-linked immunosorbent assay (cELISA) for antibodies to the pr-E protein of West Nile virus and other flaviviruses due to cross-reactivity. The overall flavivirus seroprevalence in the dog population was 70.7% (95% CI = 66.4–74.8%). At the animal level, significant associations between seropositive dogs and district location, age, breed and keeping practice were determined. At the household level, the major risk factors were rural and peri-urban locations, presence of pigs, coil burning and households without mosquito-borne disease experience (p < 0.05). Mosquito control by using larvicides or electric traps could lower seropositivity, but other measures did not contribute to significant risk mitigation of flavivirus exposure in dogs. These results will support better control of mosquito-borne diseases in Hanoi, and they indicate that dogs can be used as sentinels for flavivirus exposure.

Knowledge and practice on prevention of mosquito-borne diseases in livestock-keeping and non-livestock-keeping communities in Hanoi city, Vietnam: A mixed-method study

Mosquito-borne diseases (MBDs) are causing high morbidity and mortality for humans. Urban livestock keeping is still common in cities around the world. The animals may serve as reservoirs for zoonotic MBDs, which increase the risks for humans. Here we assess the knowledge and practices related to MBDs in households with livestock and without livestock and explore the perceptions of the health care sector about MBDs and livestock keeping in Hanoi city of Vietnam in a cross-sectional study. A quantitative survey was conducted including 513 households with and without livestock-keeping in six districts and complemented with qualitative surveys with four health staff from Hanoi Center of Disease Control and three district health centers. The quantitative survey indicated that the participants possessed basic knowledge on MBDs with an average score of 18.3 out of 35, of which non-livestock-keeping households had a better knowledge than households keeping livestock (p<0.05). Both household categories had low score, 3.5 out of 11, regarding preventive practices against MBDs. The negative binomial model showed that occupation and location of living were factors associated to the knowledge on MBDs. Farmers were likely to have better preventive practices as compared to office workers (p<0.05). Those who had better knowledge also had more adequate preventive practices against MBDs (p<0.001). The qualitative survey revealed that livestock keeping was determined as increasing risks of MBDs due to the increase of mosquito population. It is recommended that community campaigns to raise the awareness and change behavior on MBDs should be organized based on collaboration between the health sector and the veterinary sector for households with and without livestock living in central urban and peri-urban areas. Further studies are needed to confirm the association between urban livestock keeping and potential increasing risks of MBDs such as dengue and Japanese encephalitis.

Influence of socio-economic, demographic and climate factors on the regional distribution of dengue in the United States and Mexico

BACKGROUND

This study examines the impact of climate, socio-economic and demographic factors on the incidence of dengue in regions of the United States and Mexico. We select factors shown to predict dengue at a local level and test whether the association can be generalized to the regional or state level. In addition, we assess how different indicators perform compared to per capita gross domestic product (GDP), an indicator that is commonly used to predict the future distribution of dengue.

METHODS

A unique spatial-temporal dataset was created by collating information from a variety of data sources to perform empirical analyses at the regional level. Relevant regions for the analysis were selected based on their receptivity and vulnerability to dengue. A conceptual framework was elaborated to guide variable selection. The relationship between the incidence of dengue and the climate, socio-economic and demographic factors was modelled via a Generalized Additive Model (GAM), which also accounted for the spatial and temporal auto-correlation.

RESULTS

The socio-economic indicator (representing household income, education of the labour force, life expectancy at birth, and housing overcrowding), as well as more extensive access to broadband are associated with a drop in the incidence of dengue; by contrast, population growth and inter-regional migration are associated with higher incidence, after taking climate into account. An ageing population is also a predictor of higher incidence, but the relationship is concave and flattens at high rates. The rate of active physicians is associated with higher incidence, most likely because of more accurate reporting. If focusing on Mexico only, results remain broadly similar, however, workforce education was a better predictor of a drop in the incidence of dengue than household income.

CONCLUSIONS

Two lessons can be drawn from this study: first, while higher GDP is generally associated with a drop in the incidence of dengue, a more granular analysis reveals that the crucial factors are a rise in education (with fewer jobs in the primary sector) and better access to information or technological infrastructure. Secondly, factors that were shown to have an impact of dengue at the local level are also good predictors at the regional level. These indices may help us better understand factors responsible for the global distribution of dengue and also, given a warming climate, may help us to better predict vulnerable populations on a larger scale.