Emerging Infectious Diseases and Public Health Policy: Insights from Cambodia,Hong Kong and Indonesia

Emerging infectious diseases affect the health of animal and human populations, but the impact goes beyond health as it extends to political, economic, social and environmental domains, as well as inter‐state relations. Deeper understanding of these impacts aids public health authorities in their duties of protection and improvement of the health of their communities, promotion of healthy practices and research on disease, injury and threat prevention and mitigation. This empirical essay gathers insights from Cambodia, Hong Kong and Indonesia as they attempt to design and implement control and surveillance systems against avian influenza – an infectious disease.     

Iodized Salt in Cambodia: Trends from 2008 to 2014

Though the consequences of nutritional iodine deficiency have been known for a long time, in Cambodia its elimination has only become a priority in the last 18 years. The Royal Government of Cambodia initiated the National Sub-Committee for Control of Iodine Deficiency Disorders in 1996 to fight this problem. Using three different surveys providing information across all provinces, we examined the compliance of salt iodization in Cambodia over the last 6 years. Salt samples from the 24 provinces were collect at the household level in 2008 (n = 566) and 2011 (n = 1275) and at the market level in 2014 (n = 1862) and analysed through a wavelength spectrophotometer for iodine content. According to the samples collected, the median iodine content significantly dropped from 22 mg/kg (25th/75th percentile: 2/37 mg/kg) in 2011 to 0 mg/kg in 2014 (25th/75th percentile: 0/8.9 mg/kg) (p < 0.001). The proportion of non-iodized salt within our collected salt drastically increased from 22% in 2011 to 62% in 2014 (p < 0.001). Since the international organizations ceased to support the procurement of iodine, the prevalence of salt compliant with the Cambodian declined within our samples. To date, the current levels of iodine added to tested salt are unsatisfactory as 92% of those salts do not meet the government requirements (99.6% of the coarse salt and 82.4% of the fine salt). This inappropriate iodization could illustrate the lack of periodic monitoring and enforcement from government entities. Therefore, government quality inspection should be reinforced to reduce the quantity of salt not meeting the national requirement.     

Hepatitis B surface antigen seroprevalence among pre- and post-vaccine cohorts in Cambodia, 2017

Background: Hepatitis B virus (HBV) infection is highly endemic in most low income countries including Cambodia. This nationwide serosurvey was conducted to assess the impact of hepatitis B vaccination and to determine whether Cambodia met the WHO regional 2017 target of hepatitis B surface antigen (HBsAg) seroprevalence less than 1% in five-year-old children.Methods: A cross-sectional multi-stage cluster survey was conducted among children born during 2010–2012 and their mothers in Cambodia. HBsAg prevalence was estimated by rapid point-of-care testing, and demographic data, including vaccination history, was collected. Vaccine coverage in children and the prevalence of HBsAg among children and mothers was calculated taking into account the complex survey design. Factors associated with children’s failure to receive timely (within 24 h) vaccination were analysed by multivariate logistic analysis.Findings: A total of 2,520 children 5–7 years old and 2,028 mothers were recruited. In total, 78.4% of children received hepatitis B vaccination birth-dose (HepB-BD); of these, 58.7% were administered ≤ 24 h. Birth at home or “other” location were independent risk factors for children’s failure to receive timely HepB-BD. Overall HBsAg seroprevalence was 4.39% (95%CI: 3.53%–5.45%) among mothers and 0.56% (95%CI: 0.32%–0.98%) among children. The prevalence among children without hepatitis B vaccination was 4.62% (95%CI: 1.31%–14.97%). Among children with a HBsAg-positive mother, prevalence was 10.11% (95%CI: 5.41%–18.11%).Interpretation: Having achieved the 2017 target of less than 1% HBsAg prevalence among 5 years old children, Cambodia can now focus on eliminating mother-to-child transmission of HBV. Moreover, the high HBsAg prevalence among mothers suggests that routine screening with proper linkage to care and treatment is needed. Strengthening measures to improve vaccination coverage further and eliminate mother-to-child transmission by coordinated programming with other services offering additional HBV interventions will help move towards the global goal of hepatitis B elimination by 2030.Funding: As per sources of funding.     

Improvement in Smallholder Farmer Knowledge of Cattle Production,Health and Biosecurity in Southern Cambodia between 2008 and 2010

Farmer knowledge surveys were conducted in 2008 and 2010 in Cambodia to evaluate the impact of a research project studying interventions that can improve cattle production and health, including biosecurity and practices relating to risks of transmission of transboundary diseases. The project hypothesis is that by increasing the value of smallholder‐owned large ruminants through nutritional interventions and improved marketing, knowledge‐based interventions including risk management for infectious diseases such as foot‐and‐mouth disease (FMD) can be implemented into a more sustainable pathway for rural development. Between 2008 and 2010, significant improvements in farmer knowledge and attitudes were recorded in three villages in three provinces of southern Cambodia. This was achieved through participatory ‘applied field research’, ‘on the job’ training plus ‘formal’ training programmes. No cases of FMD were recorded during the study period in the ‘high‐intervention’ (HI) villages despite the common occurrence of the disease in a nearby ‘low‐intervention’ and many other villages in the three provinces. Whilst it is likely that protection of these villages from FMD infection was from increasing the herd immunity by vaccination, it could also have been partly because of a decrease in risk behaviours by farmers as a result of their increasing knowledge of biosecurity. The research indicates that smallholder farmers are motivated by nutritional interventions that improve the value of their cattle ‘bank’ and offer better marketing opportunities. This provides a more receptive environment for introduction of disease risk management for infectious and other production limiting diseases, best implemented for smallholder farmers in Cambodia by intensive training programmes. In lieu of a widespread public awareness programme to deliver mass education of smallholder farmers in disease prevention and biosecurity, livestock development projects in South‐East Asia should be encouraged to include training in disease risk management as an important intervention if the current momentum for trade in large ruminant livestock and large ruminant meat is to continue to progress and contribute to addressing global food security concerns.     

Frequency and patterns of contact with domestic poultry and potential risk of H5N1 transmission to humans living in rural Cambodia

Background Since 2004, H5N1 outbreaks have been recurrent in domestic poultry and humans in Cambodia. To date, seven human cases (100% CFR) and 22 outbreaks in poultry have been confirmed. Household ownership of backyard poultry (FAO Sector 4 poultry production) in rural Cambodia is high. An understanding of the extent and frequency of poultry handing behaviors in these settings is necessary to assess the risk associated with different practices and to formulate sensible recommendations to mitigate this risk. We collected new data from six geographic regions to examine patterns of human contact with poultry among rural farmers in Cambodia and identify populations with the highest potential exposure to H5N1. Methods and Findings A cross‐sectional survey was undertaken in which 3,600 backyard poultry owners from 115 randomly selected villages in six provinces throughout Cambodia were interviewed. Using risk assessment methods, patterns of contact with poultry as surrogate measures of exposure to H5N1 were used to generate risk indices of potential H5N1 transmission to different populations in contact with poultry. Estimates of human exposure risk for each study participant (n = 3600) were obtained by multiplying each reported practice with a transmission risk‐weighting factor and summing these over all practices reported by each individual. Exposure risk estimates were then examined stratified by age and gender. Subjects reported high contact with domestic poultry (chickens and ducks) through the daily care and food preparation practices, however contact patterns varied by gender and age. Males between the ages of 26‐40 reported practices of contact with poultry that give rise to the highest H5N1 transmission risk potential, followed closely by males between the ages of 16‐25. Overall, males had a higher exposure risk potential than females across all age groups (p < 0·001). Conclusions Our results demonstrate that most of the population in rural Cambodia is in frequent contact with domestic poultry. About half of the population in this study carried out on a regular basis at least one of the practices considered to be high risk for the effective transmission if the bird is infected. There was however substantial variation in the frequency of different practices and thus the potential risk of transmission of H5N1 from poultry to humans is not uniform across age and gender even amongst populations living in close proximity to poultry.     

Changing patterns of forest malaria among the mobile adult male population in Chumkiri District, Cambodia

Forest malaria remains a major problem in many parts of Southeast Asia and South America. In Cambodia, where a significant reduction of malaria morbidity and mortality has been observed in the last 20 years, the forest malaria situation was studied in Chumkiri District by analysing the available passive case detection data and conducting malariometric (n=1018) and questionnaire surveys (n=374) in four forest-fringe villages. There has been a decreasing trend of malaria incidence from 2001. Plasmodium falciparum was highly predominant and P. vivax was rare. The nearby-forest villages showed significantly higher parasite rates than the far-from-forest villages (9.0% vs. 1.2%, p<0.01). Malaria was highly restricted to the male adults but was nearly non-existent in other accompanying family members, including small children and females. Low income and working in forests were strongly associated with the malaria risk. Our results suggest that transmission has greatly reduced in forest-fringe villages, but remains active in forests, which is primarily maintained between the forest vector Anopheles dirus and ethnic minority inhabitants. Specific interventions directed to these previously neglected in-forest inhabitants to protect themselves and male adult villagers during their forest activities are necessary to achieve an ultimate goal of malaria elimination from Cambodia.     

Low frequency of acute hepatitis E virus (HEV) infections but high past HEV exposure in subjects from Cambodia with mild liver enzyme elevations,unexplained fever or immunodeficiency due to HIV-1 infection

BackgroundIn Cambodia, previous studies conducted on hepatitis E virus (HEV) infection are scant, sometimes old, and showed inconsistent results. Moreover, there is no data about HEV infection in Cambodian HIV-1-infected patients.ObjectivesTo assess the occurrence of acute HEV infections and the level of past HEV exposure in one Mekong country.Study designUsing anti-HEV IgM and HEV RNA detection, we retrospectively investigated the presence of acute HEV infection in 825 individuals, including 350 subjects with or without fever, 300 subjects with or without liver enzyme elevations (LEE) and 175 antiretroviral treatment (ART)-naïve, severely immunocompromised HIV-1-infected patients. The detection of anti-HEV IgG was also performed to assess ancient HEV exposure.ResultsNine individuals tested positive for anti-HEV IgM yielding an overall rate of 1.1% (95% confidence interval (CI), 0.5–2.0). We did not find significant differences for anti-HEV IgM rates between subjects with unexplained fevers (1.5%) and those with malaria or dengue-associated fever (1.7%) or non-febrile individuals (0%) (P = 0.49), and between subjects with (1.5%) and without (2.0%) LEE (P = 0.87). No HIV-infected patient tested positive for anti-HEV IgM. HEV RNA was not detected in all tested plasma specimens (n = 578). Overall, the anti-HEV IgG prevalence rate was 30.1% (95% CI, 27.0–33.2).ConclusionsThe scarcity of recent HEV infection contrasted with the high level of past HEV exposure. The role of HEV in liver disease is likely minor in Cambodia since no HEV RNA was detected in our studied populations, including HIV-positive patients with severe immunodepression.