Part 2: Biosecurity and disease management for wildlife
The African buffalo is used to illustrate the principles of disease management.
Epidemiological triangle
The epidemiology of any infectious disease involves the complex interaction between factors of the host, agent (disease) and environment known as the epidemiological triangle. Therefore, for a disease to manifest there must be a susceptible host, an infective agent, and a vector to carry the agent to the host. Basic disease control means that one of the links in this triangle has to be broken.
Disease transmission by arthropod vectors can occur by mechanical or biological means. Mechanical transmission involves the transfer of a pathogen by an external body part (e.g., legs) of the vector; the pathogen remains unchanged (i.e., does not replicate or develop further).
Most species of flies serve as mechanical vectors. Biological transmission involves the alteration of the pathogen within the vector. The vector uptakes the pathogen – usually through a blood meal from an infected animal – and the pathogen undergoes further development or replication within the arthropod vector before being transferred to a susceptible animal, usually through a bite. Midges, ticks, and mosquitoes are common biological disease vectors.
Additionally, myiasis – the infestation of the skin or wounds by fly larvae – can also be of great economic concern and can affect wildlife and domestic livestock.
Figure 1: Epidemiological Triangle
An effective biosecurity plan for wildlife includes the following elements;
How to receive and manage new animals on the ranch.
How to regulate movement on and off the ranch.
How to clean and disinfect equipment on the ranch to reduce pathogen levels.
How to monitor animal health on the ranch.
The two key biosecurity measures are:
- Minimising movement of animals, animal products, people, vehicles and equipment between premises where animals are kept.
1.1 Animals
– transfer of animals between different production groups/ areas
– dead animal disposal
– dirt, manure or contaminants
Recommended practices
All buffalo must be tested against the four compulsory diseases (foot-and-mouth disease, corridor, brucellosis and bovine tuberculosis according to the Veterinary Procedural Notice: Buffalo Disease Risk Management 17 February 2017) before being introduced onto the ranch.
All buffalo must be treated with a dip to remove ticks with the reading of the last intradermal test and with the loading process to the farm.
Close the cow herd for the 4-year breeding cycle.
No other wild animals must get into the breeding camp on the farm. Remove all antelope (specifically kudu and nyala – anthrax and tuberculosis control). Shoot Warthog for rations. Jackals can carry the foetal membranes of aborted calves into the breeding camp from the outside camps.
Baboons and vervet monkeys should not be allowed at feeding spots. These animals can act as mechanical vectors of pathogens.
Cattle on neighbouring properties must be tested for tuberculosis and brucellosis on an annual basis and the results presented to the owner.
Double fences with a 20-meter surveillance zone between them must be erected between buffalo and cattle camps. A 1-meter-high jackal-proof fence should be attached to the outside fence closest to the cattle to prevent jackals from carrying foetal membranes into the buffalo breeding camp. The outside fence must have an electric strand at the shoulder height of cattle on the outside.
Carcass disposal: The carcass should be disposed of suitably to prevent the spreading of infectious or parasitic diseases. Carcasses not suitable for human consumption should be buried at least a meter deep. The bones of dead animals should be picked up and burnt regularly to prevent botulism. Wild animals that have died of zoonosis should preferably be burnt or destroyed in an incinerator.
1.2 People
– ranch personnel and family members living on-site
– contractors, maintenance personnel, neighbours, service personnel, visitors
Recommended practices
– Staff members working directly with buffalo should be tested for human tuberculosis (GeneXpert test).
– Staff members should be trained to identify the symptoms of important diseases in buffalo.
– Staff members should be supplied with gum boots and protective clothing for the feeding period. After feeding they can use their original working clothes on the ranch.
– Veterinarians should be supplied with gum boots and protective clothing on the ranch before entering the breeding camp.
1.3 Vehicles and equipment
– Husbandry equipment (cubes, dips, licks & dart guns, etc.)
– Hirt/manure/contaminants carried on hands, boots, clothing, hair
– Dirt/manure/contaminants carried on cars, trucks, tractors, scales
Recommended practices
– The daily routine must be done by using the same vehicle for feeding animals.
– Start the feeding procedure by disinfecting the tyres of the vehicle when notifiable diseases are present in the district.
1.4 Feed, water and fences raw materials
post-production contamination or spoilage during transport and storage
faecal and urine contamination from the same species or other species
Recommended practices
– Lucerne must be obtained from a brown-ear tick-free area such as the Northern Cape.
– Fence inspection must be done every week to determine if animals such as warthog do not enter the breeding camps and feed at the same feeding spots as buffalo.
– Breaking the fence is the first line where contagious diseases can break through in a new population.
– Leaking drinking troughs can act as a reservoir for parasites that can infect their host.
- Principles used to prevent pathogens from being brought into a herd from outside sources (external biosecurity measures) include:
Restricted access to the premises where the animals are kept
Hygienic measures to ensure that people who need to enter the premises do not bring in pathogens and strict control/ decontamination of materials brought onto the ranch. Labourers must not work with domestic animals before feeding buffalo.
– Keeping a closed herd.
– Introduction of animals only from herds of known health status.
– Quarantine of newly introduced animals.
– Measures to keep out other livestock; strict separation between domestic livestock and wildlife – jackal-proof fence for creeping animals.
– Strict control over feed; no swill feeding; ensuring that feed and feed sources are wholesome and free from contaminants from manufacture through delivery and storage to consumption
– Exclusion of vectors; control of internal and external parasites – control vectors with diatomaceous earth.
Summary of the management of diseases with buffalo ranching
Conclusion
New drug combinations developed by companies such as V-Tech, simplified the translocation of wildlife, and more specifically the African buffalo. Some of the risks and high costs experienced in the past with traditional immobilization drugs are now mitigated with combination drug therapy.
This enabled the wildlife industry to move animals more freely and safely, therefore necessitating an awareness of the potential biosecurity risks involved. Veterinarians should take cognisance thereof and incorporate it into the management plans of their clients.