Long haul to crack unique rabies cycle among kudu

Wildlife conversation is increasingly becoming an important practice to protect game and preserve them for future generations. Namibia is a country rich in a wide range of wildlife resources annually attracting thousands of tourists from all over the world.
The kudu is one of Namibia’s most well-known and popular antelope species but also a species under constant threat from rabies. Rabies is a fatal viral disease and can be transmitted from one species to another. Traditionally, carnivores were the most common vectors for this disease, but since the late 1970s, following a devastating rabies outbreak in the kudu population, indications are that a possible species specific strain is now being maintained in nature by the Namibian kudu population. This serious disease not only continues to pose a threat to that population, but also to our wildlife in general, as the spread among antelopes continues.
It is estimated that, from 1977 to 1986, between 30 000 to 50 000 kudus (20% to 40% of the total polutation) died from rabies (Schneider, HP. 1994 and Hassel, R.H 1982). Studies further revealed that rabies in kudu occurs in cycles in areas with dense kudu population, starting in central Namibia, then spreading northwards to all the major habitats of kudu, including the Etosha National Park. Moreover, between 2001 – 2006, it is estimated that 104 humans died of rabies in Namibia. The main source of this infection however was the domestic dog (often feral dog), affecting many lives in the Northern Communal Areas (NCAs) of the country, affecting especially children.
Rabies in kudu and possible evidence of the existence of natural immunity in the animals requires a great deal of research. It is for this reason that the Namibia Agriculture Union (NAU) appointed Agra ProVision, under the leadership of Dr Rainer Hassel to implement the project: “An epidemiological survey of rabies in kudu and the development of an oral anti-rabies vaccine for kudu in Namibia.” The project’s phase 1 was implemented over a period of 13 months, from 1 March 2015 to 30 April 2016; seeking to find an antidote for this unique, seemingly independent rabies virus found in kudus in Namibia.
Animals can be vaccinated against rabies. However, vaccination of free roaming wildlife using traditional vaccination methods requires the use of helicopters and darting, making the process a very costly exercise with a high chance of missing individual animals. It is for this reason that the research is exploring alternative vaccination methods, drawing best practices successfully achieved in parts of Europe to vaccinate free roaming foxes using an oral bait spread over large areas.


Phase 1
The first part of the research was to collect relevant data that provided basic and essential information of the epidemiology of rabies amongst kudus in Namibia. On the practical side, the research began with identifying and capturing of kudus, and placing them in a quarantined facility about 40 kilometers north of Omaruru. This was followed by animal handling activities to collect blood samples, ear tagging for identification, deworming and administration of an oral vaccine to a number of captive kudu. The trial of administering the vaccines measured the vaccine’s effectiveness and established to what extent it can protect kudus against rabies infection. The second part of the trial aimed to prove that horizontal spread of rabies among kudus is possible, in other words how the disease can be transmitted from kudu to kudu by direct contact.
The main goal of the research project is to find an economically, yet highly viable effective and practical method of oral vaccination of kudu against rabies. The project’s phase 1 tested two methods of vaccination using two different types of vaccine viz oral and intra-muscular vaccine, to determine whether the vaccinations achieved protection for animals infected with rabies. For the oral vaccine group, the results indicated that only 3 out of 10 animals vaccinated by direct oral application of a modified live vaccine developed clinical symptoms consistent with rabies survived, after being challenged with a high dose rabies virus. In the intra-muscular vaccine group, 9 animals were vaccinated with a commercial inactivated vaccine after which all survived the high dose of rabies virus challenge. These results state that intra-muscular vaccination protects 100% of vaccinated animals against rabies infection, while oral instillation of the modified live virus currently is not proven to protect the kudu population using the method applied in the trials. Therefore, it is necessary to continue the research with a phase 2. The method of oral application of the vaccine needs to be changed and improved to induce an immune response in the vaccinated animals that will protect them against the infection.
The project’s phase 1 achieved positive results, exceeding the set objectives. A suitable bait was developed successfully and the intra-muscular vaccine trials were successfully completed. A hypothesis to prove the horizontal spread of rabies by direct contact amongst kudus was tested. The results revealed that the transmission trials performed as part of the project were not able to prove that transmission of rabies from infected to non-infected kudu by direct contact did occur. Furthermore, the project revealed evidence that the modified live vaccine can be absorbed orally and can stimulate the immune system to produce antibodies, although not sufficient to protect the animals against the rabies infection. The main reason may lie with the method used to orally vaccinate the kudu, and thus the need to re-trial such vaccinations.
There is an indication that rabies is becoming more of a problem in Namibia, and this warrants the continuation of the project with phase 2. Phase 2 will be implemented with the main objective to develop an effective and practical method of oral vaccination of kudu against rabies and to determine the duration of immunity of animals in the intra-muscular vaccine group. The proposed phase will cost an estimated N$2.8 million. If phase 2 is not realised, the negative ecological, economic and health impact that a rabies outbreak can have on the agriculture and tourism community of Namibia, can be considerable.


KASSIE
In a nutshell
·Kudu rabies in Namibia was first identified in the late 1970s.
·Rabies is a serious fatal viral infection posing a threat to the kudu population.
·The research aims to find an antidote for kudu rabies in Namibia and eventually have a vaccine against the disease.
·Kudus are very important resources in keeping an ecological balance in the agriculture sector and form an integral part of on-farm income, thereby also contributing to foreign exchange earnings nationally.
·The project’s phase 1 was successfully completed, albeit the proof for oral vaccination efficacy needs to be established. Thus, phase 2 will develop a method of oral vaccination.
*This article is contributed by AgraProvision.