Recent research - February 2017

A round-up of recent research articles in line with GARC's mission.

 

PEP

Role of systemic injection of rabies immunoglobulin in rabies vaccination. The role of systemic injection of rabies immunoglobulin (RIG) in rabies vaccination was investigated in a mouse model. Analyzing anti-rabies virus antibody levels in the serum of mice given various doses of RIG combined with rabies vaccine, the results showed that systemic injection of RIG does not contribute detectably to passive or adaptive immunization. Thus the main function of RIG is to neutralize rabies virus by local infiltration of the wound.

Laboratory testing

A Comparative Study of the RAPINA and the Virus-Neutralizing Test (RFFIT) for the Estimation of Antirabies-Neutralizing Antibody Levels in Dog Samples.The rapid neutralizing antibody test (RAPINA) is a novel, immunochromatographic test that uses inactivated virus to quantify anti-rabies antibodies, avoiding cell culture and the use of live virus. The vaccination status of 1135 dogs in the Philippines, Thailand and Japan were analysed by the RAPINA and compared to the standard RFFIT test. The RAPINA results were highly homologous and reproducible among different laboratories, suggesting that this test is appropriate to survey vaccination coverage in countries with limited resources.

Inactivation of Rabies Virus. Various reagents for the effective inactivation of rabies virus were tested. Virkon S (1%) solution effectively reduced rabies virus in culture medium supplemented with 10% foetal calf serum within 1 minute. Isopropyl alcohol (70%) is a suitable agent for surface decontamination whereas 70% ethanol was ineffective. Rabies virus  was also inactivated when cell cultures were fixed with 3% or 4% paraformaldehyde for 30minutes.

Surveillance / Diagnosis

Development and validation of sensitive real-time RT-PCR assay for broad detection of rabies virus. Two real-time quantitative RT-PCR assays were developed for large-spectrum detection of RABV, with a focus on African isolates. The primer and probe sets targeted highly conserved regions of the nucleoprotein (N) and polymerase (L) genes. No non-specific amplification or cross-reaction with a range of other viruses was found. The effective detection and high sensitivity of these assays on African isolates showed that they can be successfully used for general research and in diagnosis and surveillance using a double-check strategy.

A Pan-Lyssavirus Taqman Real-Time RT-PCR Assay for the Detection of Highly Variable Rabies virus and Other Lyssaviruses. A newly developed multiplex real-time RT-PCR assay named LN34, uses degenerate primers and probes along with probe modifications to achieve superior coverage of the Lyssavirus genus while maintaining sensitivity and specificity. The LN34 assay was able to detect all RABV variants and other lyssaviruses in a validation panel. It can be quickly adapted in a laboratory to enhance the capacity of rabies molecular diagnostics, especially in rural areas.

Epidemiology

Re-emerging of rabies in Shaanxi Province, China, 2009 to 2015. Sequencing of virus from 269 human rabies cases revealed viral migration paths from Sichuan, Guizhou and Hunan to the Hanzhong prefecture of Shaanxi and then further spread to Xi'an and other prefectures.

Human Rabies - Puerto Rico, 2015. The first reported case of human rabies associated with a mongoose bite in North America. A 54 year old Puerto Rican man died in early December after an untreated bite from a mongoose during the first week of October.

Quantitative risk assessment of the introduction of rabies into Japan through the importation of dogs and cats worldwide.The risk of rabies introduction into Japan through international importation of dogs and cats was quantified, using a stochastic scenario tree model. The number of years until the introduction of a rabies case was estimated to be 49,444 years, suggesting that current import controls are effective. Modelling suggested some simplification could be justified, but that serological testing should not be stopped. Non-compliance or smuggling activities could substantially increase the risk of rabies introduction, so compliance must be promoted.

The Epidemiological Importance of Bats in the Transmission of Rabies to Dogs and Cats in the State of São Paulo, Brazil, Between 2005 and 2014. In São Paulo, Brazil the rabies virus lineage associated with dogs has not been found since 1998. Rabies cases in dogs and cats in São Paulo between 2005 and 2014 were investigated. Sequencing of the N gene nucleotide sequences  from ten samples from dogs and cats revealed that the viruses in all samples were those circulating in Brazilian bats.

Mass Dog Vaccination

Optimal frequency of rabies vaccination campaigns in Sub-Saharan Africa. While previous studies have considered optimal coverage of animal rabies vaccination, variation in the frequency of vaccination campaigns has not been explored. A rabies virus transmission model was parameterised for two districts of northwest Tanzania, Ngorongoro (pastoral) and Serengeti (agro-pastoral). We found that optimal vaccination strategies were every 2 years, at 80% coverage in Ngorongoro and annually at 70% coverage in Serengeti and the optimality of these strategies was sensitive to the rate of rabies reintroduction from outside the district. Coordinated campaigns may provide monetary savings in addition to public health benefits.

Dog ecology

Ecology and Demography of Free-Roaming Domestic Dogs in Rural Villages near Serengeti National Park in Tanzania. For four years, 2,649 free-roaming domestic dogs in four rural villages in Tanzania (two villages with and two without a rabies vaccination campaign) were examined for body condition, sex, age, survivorship and reproduction. Overall survival was related to body condition, and in one non-vaccination village survival was lower than in the other three villages, all of which were similar. Within vaccination villages, vaccinated dogs had higher survivorship than unvaccinated dogs. Dog population growth was similar in all the villages suggesting village characteristics and ownership practices likely have a greater impact on overall dog population dynamics than vaccination.

Advocacy

Novel Financing Model for Neglected Tropical Diseases: Development Impact Bonds Applied to Sleeping Sickness and Rabies Control. A discussion of the potential for Development Impact Bonds to speed up progress to rabies elimination.