Using Integrated Bite Case Management to estimate the burden of rabies and evaluate surveillance in Oriental Mindoro, Philippines

Background

Despite national elimination efforts, dog-mediated rabies remains endemic in the Philippines. Free provision of post-exposure prophylaxis (PEP) through the widespread establishment of Animal Bite Treatment Centers (ABTCs) has improved accessibility; however, the resulting upsurge in PEP demand is not sustainable, and human rabies deaths continue. Dog vaccination coverage also remains inadequate, and it is unclear whether surveillance is effective.

Methods

Here, we used Integrated Bite Case Management (IBCM) to collect enhanced rabies surveillance data in Oriental Mindoro Province over a 3-year period (2020-2022). Adapting a probabilistic decision tree model, we estimated the burden of rabies, evaluated surveillance performance, and analyzed the costs and benefits of current rabies prevention and control practices in the province.

Results

The incidence of bite patients receiving PEP was high in Oriental Mindoro Province (1,246/100,000 persons/year), though < 3% of presenting patients were deemed high-risk for rabies exposure (24/100,000 persons/year). Using a decision tree model, we estimated that around 73.8% of probable rabies-exposed patients sought PEP (95% Prediction Interval, PrI: 59.4%-81.1%) and that routine surveillance confirmed < 2% of circulating animal rabies cases, whereas IBCM resulted in a nearly fourfold increase in case detection. Furthermore, we estimated that an average of 560 (95% PrI 217-1,090) dogs may develop rabies annually in the province, equating to 3-5 cases per 1,000 dogs per year. On average, 20 to 43 human deaths were averted by PEP each year in Oriental Mindoro at an annual cost of $582,110 USD (i.e., $51.44 USD per person) or $20,190 USD (95% PrI $11,565-79,400) per death averted.

Conclusion

While current practices for PEP provisioning in the Philippines have improved access, a large proportion of people exposed to rabies (> 26%, 95% PrI 18.8%-40.1%) are still not seeking healthcare. Integrating an intersectoral surveillance system, such as IBCM, into national policy could greatly improve case detection if well implemented, with further benefits extending to guidance for PEP administration, potentially reducing unnecessary expenditure on PEP, and situational awareness to inform control of rabies through mass dog vaccination.

A Comparative Study of the RAPINA and the Virus-Neutralizing Test (RFFIT) for the Estimation of Antirabies-Neutralizing Antibody Levels in Dog Samples

The mass vaccination of dogs against rabies is a highly rational strategy for interrupting the natural transmission of urban rabies. According to the World Organization for Animal Health (OIE) and the World Health Organization (WHO), the immunization of at least 70% of the total dog population minimizes the risk of endemic rabies. Knowledge of the virus-neutralizing antibody (VNA) level against the rabies virus (RABV) is required to evaluate protective immunity and vaccine coverage of dogs in the field. The rapid focus fluorescent inhibition test (RFFIT) and the fluorescent antibody virus neutralization (FAVN) test are recommended by OIE and WHO to determine the VNA levels in serum. However, these tests are cell culture based and require the use of live viruses and specialized equipment. The rapid neutralizing antibody test (RAPINA) is a novel, immunochromatographic test that uses inactivated virus to estimate the VNA level qualitatively. It is a simple, rapid and inexpensive, although indirect, assay for the detection of VNA levels. The RAPINA has shown good positive and negative predictive values and a high concordance with the RFFIT results. In this study, we compared the performance of the two tests for evaluating the vaccination status of dogs in the Philippines, Thailand and Japan. A total of 1135 dog sera were analysed by the RAPINA and compared to the VNA levels determined by the RFFIT. The overall positive and negative predictive values of the RAPINA were 96.2-99.3% and 84.5-94.8%, respectively, with a concordance (kappa) of 0.946-0.97 among the three countries. The RAPINA results were highly homologous and reproducible among different laboratories. These results suggest that this test is appropriate to survey vaccination coverage in countries with limited resources.

Willingness to Pay for Dog Rabies Vaccine and Registration in Ilocos Norte, Philippines (2012)

BACKGROUND

The Philippines is one of the developing countries highly affected by rabies. Dog vaccination campaigns implemented through collaborative effort between the government and NGOs have played an important role in successfully reducing the burden of disease within the country. Nevertheless, rabies vaccination of the domestic animal population requires continuous commitment not only from governments and NGOs, but also from local communities that are directly affected by such efforts. To create such long-term sustained programs, the introduction of affordable dog vaccination and registration fees is essential and has been shown to be an important strategy in Bohol, Philippines. The aim of this study, therefore, was to estimate the average amount of money that individuals were willing to pay for dog vaccination and registration in Ilocos Norte, Philippines. This study also investigated some of the determinants of individuals' willingness to pay (WTP).

METHODS

A cross-sectional questionnaire was administered to 300 households in 17 municipalities (out of a total of 21) selected through a multi-stage cluster survey technique. At the time of the survey, Ilocos Norte had a population of approximately 568,017 and was predominantly rural. The Contingent Valuation Method was used to elicit WTP for dog rabies vaccination and registration. A 'bidding game' elicitation strategy that aims to find the maximum amount of money individuals were willing to pay was also employed. Data were collected using paper-based questionnaires. Linear regression was used to examine factors influencing participants' WTP for dog rabies vaccination and registration.

KEY RESULTS

On average, Ilocos Norte residents were willing to pay 69.65 Philippine Pesos (PHP) (equivalent to 1.67 USD in 2012) for dog vaccination and 29.13PHP (0.70 USD) for dog registration. Eighty-six per cent of respondents were willing to pay the stated amount to vaccinate each of their dogs, annually. This study also found that WTP was influenced by demographic and knowledge factors. Among these, we found that age, income, participants' willingness to commit to pay each year, municipality of residency, knowledge of the signs of rabies in dogs, and number of dogs owed significantly predicted WTP.

Genetic diversity and geographic distribution of genetically distinct rabies viruses in the Philippines

Background

Rabies continues to be a major public health problem in the Philippines, where 200–300 human cases were reported annually between 2001 and 2011. Understanding the phylogeography of rabies viruses is important for establishing a more effective and feasible control strategy.

Methods

We performed a molecular analysis of rabies viruses in the Philippines using rabied animal brain samples. The samples were collected from 11 of 17 regions, which covered three island groups (Luzon, Visayas, and Mindanao). Partial nucleoprotein (N) gene sequencing was performed on 57 samples and complete glycoprotein (G) gene sequencing was performed on 235 samples collected between 2004 and 2010.

Results

The Philippine strains of rabies viruses were included in a distinct phylogenetic cluster, previously named Asian 2b, which appeared to have diverged from the Chinese strain named Asian 2a. The Philippine strains were further divided into three major clades, which were found exclusively in different island groups: clades L, V, and M in Luzon, Visayas, and Mindanao, respectively. Clade L was subdivided into nine subclades (L1–L9) and clade V was subdivided into two subclades (V1 and V2). With a few exceptions, most strains in each subclade were distributed in specific geographic areas. There were also four strains that were divided into two genogroups but were not classified into any of the three major clades, and all four strains were found in the island group of Luzon.

Conclusion

We detected three major clades and two distinct genogroups of rabies viruses in the Philippines. Our data suggest that viruses of each clade and subclade evolved independently in each area without frequent introduction into other areas. An important implication of these data is that geographically targeted dog vaccination using the island group approach may effectively control rabies in the Philippines.

Rabies continues to be a major public health problem in the Philippines. We conducted a molecular epidemiological study of rabies using the complete glycoprotein (G) gene from 235 animal brain samples collected in the Philippines between 2004 and 2010. We identified three major clades and two distinct genogroups in the Philippines. The three major clades L, V, and M were found specifically in the Luzon, Visayas, and Mindanao island groups, respectively. Additionally, two minor genogroups were located in the Luzon island group. These data suggest that although human mediated transmission may have occurred, these virus clades evolved independently after a single introduction into each island group. All of the analyzed Philippine strains were clustered into Asian 2b, which diverged from the Chinese strain Asian 2a. No recent introduction of rabies into the Philippines from other countries was apparent. The elimination of rabies by 2020 is a national goal in the Philippines, necessitating urgent development of a more effective and feasible strategy for controlling rabies. Our findings indicate that a geographically targeted dog vaccination campaign may effectively control rabies in island nations such as the Philippines.

Implementation of an intersectoral program to eliminate human and canine rabies: the Bohol Rabies Prevention and Elimination Project

BACKGROUND

The province of Bohol, located in the Visayas islands region in the Philippines has a human population of 1.13 million and was the 4th highest region for human rabies deaths in the country, averaging 10 per year, prior to the initiation of the Bohol Rabies Prevention and Elimination Project (BRPEP).

AIMS

The BRPEP was initiated in 2007 with the goal of building a sustainable program that would prevent human rabies by eliminating rabies at its source, in dogs, by 2010. This goal was in line with the Philippine National Rabies Program whose objective is to eliminate rabies by 2020.

METHODS

The intersectoral BRPEP was launched in 2007 and integrated the expertise and resources from the sectors of agriculture, public health and safety, education, environment, legal affairs, interior and local government. The program included: increasing local community involvement; implementing dog population control; conducting mass dog vaccination; improving dog bite management; instituting veterinary quarantine; and improving diagnostic capability, surveillance and monitoring. Funding was secured from the national government, provincial, municipal and village units, dog owners, NGOs, the regional office of the WHO, the UBS Optimus Foundation, and the Global Alliance for Rabies Control. The BRPEP was managed by the Bohol Rabies Prevention and Eradication Council (BRPEC) under the jurisdiction of the Governor of Bohol. Parallel organizations were created at the municipal level and village level. Community volunteers facilitated the institution of the program. Dog population surveys were conducted to plan for sufficient resources to vaccinate the required 70% of the dogs living in the province. Two island-wide mass vaccination campaigns were conducted followed by "catch up" vaccination campaigns. Registration of dogs was implemented including a small fee that was rolled back into the program to maintain sustainability. Children were educated by introducing rabies prevention modules into all elementary schools in Bohol. Existing public health legislation at the national, provincial, and municipal level strengthened the enforcement of activities. A Knowledge, Attitude and Practices (KAP) survey was conducted in 2009 to evaluate the educational knowledge of the population. Increased surveillance was instituted to ensure that dogs traveling into and out of the province were vaccinated against rabies. Human and animal cases of rabies were reported to provincial and national authorities.

KEY RESULTS

Within the first 18 months of the BRPEP, human rabies deaths had decreased annually from 0.77 to 0.37 to zero per 100,000 population from 2007-2009. Between October 2008 and November 2010 no human and animal cases were detected. Increased surveillance on the island detected one suspected human rabies case in November 2010 and one confirmed case of canine rabies in April 2011. Two mass vaccination campaigns conducted in 2007 and 2008 successfully registered and vaccinated 44% and 70% of the dogs on the island. The additional surveillance activities enabled a mobilization of mop up vaccination activities in the region where the human and canine case was located. Due to the increased effective and continuous surveillance activities, rabies was stopped before it could spread to other areas on the island. The program costs totaled USD 450,000. Registration fees collected to maintain the program amounted to USD 105,740 and were re-allocated back into the community to sustain the program.

Reston ebolavirus in humans and animals in the Philippines: a review

The 2008 Reston ebolavirus infection event in domestic pigs has triggered continuing epidemiologic investigations among Philippine health and veterinary agencies in collaboration with international filovirus experts. Prior to this, there were only 3 known and documented Reston ebolavirus outbreaks in nonhuman primates in the world, all traced back to a single geographic source in the Philippines in a monkey breeding/export facility. The first one in 1989 was the first-ever Ebola virus that emerged outside of Africa and was also the first known natural infection of Ebola virus in nonhuman primates. When it was first discovered among laboratory monkeys in the United States, the source was immediately traced back to the farm located in the Philippines. The second outbreak was in 1992-93. The third episode in 1996 was the last known outbreak before Reston ebolavirus reemerged in pigs in 2008. The isolated outbreaks involving 2 animal species bring forth issues requiring further investigations, and highlight the significance of intersectoral collaboration to effectively address zoonoses prevention and control/response in the interest of minimizing public health risk.

The origin and phylogeography of dog rabies virus

Rabies is a progressively fatal and incurable viral encephalitis caused by a lyssavirus infection. Almost all of the 55 000 annual rabies deaths in humans result from infection with dog rabies viruses (RABV). Despite the importance of rabies for human health, little is known about the spread of RABV in dog populations, and patterns of biodiversity have only been studied in limited geographical space. To address these questions on a global scale, we sequenced 62 new isolates and performed an extensive comparative analysis of RABV gene sequence data, representing 192 isolates sampled from 55 countries. From this, we identified six clades of RABV in non-flying mammals, each of which has a distinct geographical distribution, most likely reflecting major physical barriers to gene flow. Indeed, a detailed analysis of phylogeographic structure revealed only limited viral movement among geographical localities. Using Bayesian coalescent methods we also reveal that the sampled lineages of canid RABV derive from a common ancestor that originated within the past 1500 years. Additionally, we found no evidence for either positive selection or widespread population bottlenecks during the global expansion of canid RABV. Overall, our study reveals that the stochastic processes of genetic drift and population subdivision are the most important factors shaping the global phylogeography of canid RABV.

Histopathology of natural Ebola virus subtype Reston infection in cynomolgus macaques during the Philippine outbreak in 1996

We investigated the livers, spleens, kidneys and lungs collected from 24 cynomolgus macaques (Macaca fascicularis) naturally infected with Ebola virus subtype Reston (EBO-R) during the Philippine outbreak in 1996, in order to reveal the histopathologic findings. These macaques showed necrotic hepatocytes with inclusions, slight to massive fibrin deposition in splenic cords, depletion of lymphoid cells in the white pulp of the spleen, and fibrin thrombi in some organs. Immunohistochemical analysis using anti-leukocyte antigen L1 antibody revealed an increase in blood-derived macrophages/monocytes in the livers, kidneys and lungs of EBO-R infected macaques. EBO-R NP antigens were detected in the macrophages/monocytes, endothelial cells and fibroblasts in the liver, spleen, kidney and lung. These results indicate that EBO-R infection is characterized by systemic coagulopathy and an increase in blood-derived macrophages/monocytes in accordance with the EBO-R propagation in macrophages/monocytes.

Chronological and spatial analysis of the 1996 Ebola Reston virus outbreak in a monkey breeding facility in the Philippines

To describe the transmission pattern of natural infection with Ebola Reston (EBO-R) virus in a breeding colony, the chronological and spatial analysis of mortality during the 1996 EBO-R virus outbreak was done in this study. The EBO-R virus infection among monkeys in the facility was widespread. Over a period of 3 months, 14 out of 21 occupied units were contaminated with antigen positive animals. A large number of wild-caught monkeys were involved in this outbreak suggesting that wild-caught monkeys have a high susceptibility to EBO-R virus infection. In this outbreak, morbidity patterns for individual animal units were very different regardless of the type and size of cages, individual or gang cages. The results suggest that not only the cage size but also poor animal husbandry practices may be risk factors for the spread of EBO-R infection.