Game is becoming more valuable and therefore, stocked at higher densities on smaller properties; disease prevention has become an important part of game ranch management (Bester 2002). Prevention of disease and parasite management is important part of wildlife management. When a disease breaks out in nature, it is usually an indication of an ecological disturbance. The study of causative factors and distribution of disease is known as epidemiology. For a disease to break out there must be a susceptible host, an infective agent and a vector to carry the agent to the host. When disease management is planned, it should be arranged and done properly. Planning should be arranged and done properly. Planning should be aimed at achieving maximum effectiveness with ecological disturbance. Target animals should therefore, not merely be vaccinated with the existing vaccine because it is cheap and effective. An ecological approach may well yield even better results (Du Toit 2002).
Anthrax is very infectious and easily transmitted. It is caused by the bacterium bacillus anthracis that form spores when it is exposed to the atmosphere. It therefore, thrives in anaerobic conditions (Du Toit, Penzhorn and Van Heerden 2002). Anthrax is a zoonotic disease with a worldwide distribution and herbivores are the natural host. Humans are incidentally infected by contact with contaminated animals or animal products. Anthrax can be transmitted from animal to animal or from animal to human (Jamie 2002). Cutting up anthrax carcasses is forbidden because the environment becomes contaminated by the release of large numbers of spores. The bacteria are not resistant to stomach juices, high environmental temperatures or decomposition of the carcass, but the spores are exceptionally hardy and can survive for many years in the soil or in old bones (Du Toit, Penzhorn and Van Heerden 2002). Soil is the reservoir for the anthrax spores, which can remain dormant for decades. Herbivores, the natural hosts, can become infected by ingesting the soil (Jamie 2002). All mammals, including humans, are possible hosts but kudu, giraffe and buffalo appear to be exceptionally susceptible to anthrax (Du Toit, Penzhorn and Van Heerden 2002). Anthrax in an animal may be recognized by one of the following (Du Toit, Penzhorn and Van Heerden 2002): · sudden death, the animal dies suddenly without displaying and clinical signs · acute depression and the loss of appetite · bloody secretions from body orifices, such as the nose and anus · swellings of the skin, especially on the throat The bacteria produce a toxin that creates conditions in the body that are favourable for the multiplication of the bacteria. They also cause a breakdown of the defence mechanisms of the body; the animal then dies of secondary shock. The sudden death of a large number of animals, especially those that occur in herds, should be regarded as suspicious. Sick animals can be treated with penicillin (Du Toit, Penzhorn and Van Heerden 2002). The following control measures are recommended (Du Toit, Penzhorn and Van Heerden 2002): · immunize all cattle and wild herbivores · trace carcasses as quickly as possible and burn or burry them · on hunting ranches near anthrax areas, trace wounded animals and remove them so as not to attract contaminated vultures in the area · supply supplementary mineral licks to prevent osteophagy (chewing on bones because of a phosphate deficiency) Water sources and soil are contaminated by the carcasses of animals that have died from anthrax. The dung of certain predators, such as the spotted hyaena Crocuta crocuta, can also contaminate the environment after they have fed on an anthrax victim. Vultures apparently spread the disease mechanically from carcasses to those water sources where the birds drink and bathe. Flies that feed on contaminated carcasses will vomit the spores onto vegetation at a height of 1 to 2 m above the ground. Animals that roll in the mud, such as buffalo Syncerus caffer and warthog, can spread the spores mechanically to the mud at waterholes. It is known that bones from contaminated carcasses have start outbreaks of anthrax (Du Toit, Penzhorn and Van Heerden 2002).
This disease is caused by various species of the genus Mycobacterium, but Mycobacterium bovis is probably the most important affecting wild herbivores. Other species that also cause tuberculosis are Mycobacterium tuberculosis and Mycobacterium avium (Du Toit, Penzhorn and Van Heerden 2002). Tuberculosis was first diagnosed in African buffalo in South Africa’s Kruger National Park in 1990. Over the past 15 years the disease has spread northwards leaving only the most northern buffalo herds unaffected. Wildlife tuberculosis has also been diagnosed in several adjacent private game reserves and in the Hluhluwe-iMfolozi Park, the third largest game reserve in South Africa. Evidence suggests that 10 other small and large mammalian species, including large predators, are spill over hosts (Michel, Keet, Kriek, Penrith and Huchzermeyer2006). An infected wild animal population can be classed as either a maintenance or spill over host, depending on the dynamics of the infection. In a maintenance host, infection can persist by intraspecies transmission alone, and may also be the source of infection for other species. In a spill over host, infection will not persist indefinitely unless there is re-infection from another species. However, transmission from a spill over host to domestic livestock may also occur. Therefore, maintenance and spill over hosts may both act as disease vectors (Corner 2006). Wildlife species on Highlands Wildernis Game Ranch that can act as spill over hosts or in which Mycobacterium. bovis infection has been confirmed are kudu, warthog, impala and honey badger. The disease is transmitted in droplets that are released when affected animals cough. A susceptible host then inhales the contaminated droplets. Other excretory products such as urine, faeces and milk also carry the bacteria and can contaminate the food and water of wild animals. Buffalo and kudu are highly susceptible (Du Toit, Penzhorn and Van Heerden 2002). Kudu appear to be the only species which show distinct clinical signs of bovine tuberculosis characterized by bilateral abscessation of parotid lymph nodes, frequently accompanied by formation of draining fistulae (Michel et al. 2006). A bacterium that is inhaled is taken up into the lung tissue by the defensive cells of the body. Other cells will be attracted by chemical substances to the site of inflammation. Tissue that dies usually calcifies to form the typical tuberculosis lesion that can be detected by post-mortem examination. The clinical signs vary, depending on the virulence of the organism, its route of infection and the stage of infection (Du Toit, Penzhorn and Van Heerden 2002). The general clinical signs are (Du Toit, Penzhorn and Van Heerden 2002): · coughing · enlarged lymph nodes or glands · weight loss and a coarse coat in chronic cases Wild animals show few clinical signs of tuberculosis and when they do, the disease is usually in an advanced stage. The treatment of wild animals is impractical and not recommended. Control measures include the following (Du Toit, Penzhorn and Van Heerden 2002): · limit the movement or relocation of susceptible animals, specially buffalo and kudu, from ranches where tuberculosis occurs in wild or domestic herbivores · in areas neighbouring cattle ranches, or where wild and domestic animals are kept on the same ranch, the cattle should be tested annually · wild animals that appear emaciated and have a rough coat should be shot and an autopsy conducted by a state veterinarian A major problem currently is the lack of a reliable diagnostic test and an effective tuberculosis vaccine for use in wild animals (Du Toit, Penzhorn and Van Heerden 2002). Once bovine tuberculosis has established itself in a native, free-ranging maintenance host, eradication of the disease becomes highly unlikely. The choice of suitable control measures depends on the primary objectives for the particular ecosystem (Michel et al. 2006).
Heartwater is a disease of ruminants caused by Ehrlicia (Cowdria) ruminantium and is transmitted by the bont tick Amblyomma hebraeum. Heartwater causes high mortality in domestic ruminants (cattle, sheep and goats) in sub-Saharan Africa and in the eastern Caribbean (Peter, Burridge and Mahan 2002). The susceptibility of wild ungulates to heartwater varies. Generally they are much less susceptible to the disease than domestic livestock. Wild susceptible animals that occur on Highlands Wildernis Game Ranch are blue wildebeest, giraffe, kudu and warthog. These animals do not show clinical signs except for the blesbok in which the disease is of a transitory nature. In per acute cases in domestic ruminants, the infected animal can die suddenly without showing any clinical signs of the disease. In acute cases the rectal temperature is high, the animal is oversensitive, breathes rapidly, and shallowly and it can display deviant behaviour. Nervous signs include continual grinding of the teeth, backward extension of the neck (torticollis), rapid eye movements and continuous muscular tremors. Tick control can reduce the occurrence of this disease considerably, especially in cases where cattle are allowed to graze in the same camp as wild ungulates (Du Toit, Penzhorn and Van Heerden 2002). In wildlife, clinical symptoms are difficult to monitor and could be rare in certain species as a result of innate resistance. Furthermore, techniques for brain biopsy on wild species are not well established and are cumbersome and dangerous, restricting their use as confirmatory tests. Diagnostic uncertainty is increased by the inconsistent occurrence of gross lesions (Peter et al. 2002).
African horse sickness
The African horse sickness (AHS) orbiviruses are non-contagious, vector borne, and principally affect equids. The viruses appear to have originated in Africa, and their effects were first recognized when susceptible horses were used during the exploration of central Africa in 1569 (Alexander, Kat, House, O’brien, Laurenson, McNutt and Osburn 1995).Zebra have long been considered the natural vertebrate host and reservoir of African horse sickness and are thought to be vital in the persistence of the virus in Africa. Zebras do not exhibit any clinical signs of infection (Van Vuuren 2006). African horse-sickness is a non-contagious viral disease affecting members of the horse and zebra family (Du Toit, Penzhorn and Van Heerden 2002). According to Alexander et al. (1995) the host spectrum of AHS viruses is known to include mammals other than equids; camelids, bovids, african elephants, and domestic dogs have been found positive for AHSV antibodies and/or viruses. The role of these non-equid hosts in the epizootiology of the disease is not well understood, and their capacity to spread the disease has occasionally been dismissed. When dogs eat the meat of animals that have died from African horse-sickness, they can also contract the disease. It is unknown whether other carnivores are also susceptible to African horse-sickness but, as a precaution, the meat of animals that have died from this disease should not be fed to carnivores (Du Toit, Penzhorn and Van Heerden 2002). While Culicoides biting midges are generally considered to be the main vector, mosquitoes and ticks have also been identified as potential AHSV vectors. The brown dog tick, Rhipicephahs sanguineus, transmitted AHS viruses from dogs to horses and vice versa (Alexander et al. 1995). Horses can be vaccinated against the disease (Du Toit, Penzhorn and Van Heerden 2002).
African swine fever
Only species of the pig family Suidae are susceptible to infection with African swine fever (Van Vuuren 2006). There are two wild members of the family Suidae in Africa; the warthog Phacochoerus africanus, the bushpig Potamochoerus harvatus (Anderson et al. 1998). It is an important disease of domestic pigs produced by an icosahedral double stranded DNA virus classified into the Asfarviridae family, genus Asfivirus (Gonzague 2002). African swine fever is a highly contagious and deadly viral disease in domestic pigs. Warthogs and bushpigs Potamochoerus harvatus, who act as carrier of the virus, do not develop clinical signs of the disease. Domestic pigs are infected by ingesting the infected tissue of a wild pig, or following the bite of an infected warthog tampan Ornithodoros porcinus. These tampans live in the burrows of warthogs and play an important role in the epidemiology of the disease. Although warthogs cannot transmit the disease directly to domestic pigs, they do distribute the tampan and are therefore important indirect carriers of the disease. In the per acute form of the disease, pigs are usually found dead. In the acute form, pigs are feverish, stop eating, become weak and walk unsteadily. Before they die, they suffer from vomiting, a bloody diarrhoea, purulent secretions from the nose and eyes and a bluish discoloration of the ears, feet and tail. In the sub acute form of the disease, abortions can occur and subsequently infections may result in death three to four weeks later. The chronic or protracted form of the disease is more difficult to recognize, because the clinical signs may correspond closely to those of other diseases. These include pneumonia, anorexia, inflammation of the joints and raw skin sores (Du Toit, Penzhorn and Van Heerden 2002). African swine fever is a controlled disease. Control measures include restriction of the movement of domestic and wild pigs and the products from these animals. It also involves the extermination of all affected pigs and those with which they had possibly been in contact. Particular care has to been taken to prevent contact between wild and domestic pigs (Du Toit, Penzhorn and Van Heerden 2002).
Foot – and mouth disease
This disease is highly contagious in cloven-hoofed animals and is caused by a virus. Although the virus can be transmitted by ingestion, infection mainly occurs by inhalation. In the endemic areas in South Africa, buffalo are regarded as important carriers of the virus. The African Buffalo is the only free-living species known to be capable of sustaining FMD infections for indefinite periods (Van Vuuren 2006). Although FMD is known as a disease of cloven-footed animals it can occur naturally in other animals, e.g., the hedgehog (Erinaceus spp.), and infection has been established experimentally in a number of other species. However, it is doubtful whether these animals play any part in the epidemiology of the disease FMD is not considered zoonotic. Although clinical cases have been proven in human, these are extremely rare in relation to human exposure during outbreaks (Davies 2002). The classic form of this disease is characterized by the formation of vesicles on the tongue, gums and mouth cavity, on the skin of the nose, between and above the hooves and on the teats and udder. The vesicles break open and raw sores or lesions develop, causing large areas of mucous membrane or skin to die off. Secondary bacterial infections may complicate the viral infection. Infected animals are depressed and feverish and show excessive salivation and lameness (Du Toit, Penzhorn and Van Heerden 2002). There is a rise in body temperature of some 3 to 4 °C (Davies 2002). The degree of seriousness of the disease varies amongst the different types of cloven-hoofed animals. Although large numbers of animals are usually affected, the mortality rate is normally quite low. Death generally occurs from infection of the heart muscle, or from secondary infections (Du Toit, Penzhorn and Van Heerden 2002). Several factors determine the epidemiology of the disease and therefore the control measures. These factors are (Davies 2002): · the incubation period · the infectious period and the quantity of virus particles expelled · the spread of virus by aerosol · the survival of virus in fomites · the persistence of the virus in carcases · the existence of carriers · the density of the host populations Foot- and mouth-disease is controlled. When the disease is suspected, it should therefore be reported immediately to the nearest state veterinarian, police station or magistrate. Under no circumstances may samples of the animals be collected and dispatched without the permission of a state veterinarian. Control generally includes strict quarantine measures, eradication or culling programme, and the immunization of all ruminants in the area (Du Toit, Penzhorn and Van Heerden 2002). According to Davies (2002) there are two approaches to controlling or eradicating FMD: slaughter and vaccination. Slaughter may be used on its own or in some combination with vaccination. All control programmes must include strict controls on the movement of animals (Davies 2002). The most important factor in the dissemination of FMD in Africa is animal movement. Success in controlling FMD in Africa is dependent as much on effective animal movement control as on the use of potent vaccines (Rweyemamu 1984).
Parasites and control
The game ranching industry progressively expands in southern Africa, the demand for translocation of wildlife for stocking existing and new enterprises is increasing exponentially. As land use practices have and are changing from conventional livestock farming to commercial wildlife-based activities, the interface between wildlife and livestock is also expanding. This in itself has an inherent disease risk, due to the fact that most Afro-endemic wildlife maintained infections, which are “silent” in their traditional hosts, may inadvertently be transported into close proximity with livestock. Conversely, certain foreign animal diseases cycling in domestic livestock may cross the interface and infect wildlife. The translocation of any animal is, in fact, the translocation of a “biological package” consisting of the host together with its attendant macro and micro parasites (Bengis 2004). Parasites are found on, and in, all wild animals. Parasites management and control are important parts of wildlife ranch management. Neglecting this will not only harm animals, but could have also have serious ecological and economic consequences. The game ranch manger must be aware and be able to notice the parasites that may occur on and in wild animals. Parasites are organisms that are dependent on a host to a greater or lesser degree. They live on, or in, a host for their entire life or a part of it, without necessarily adversely affecting the host. The parasites of wild animals can be divided into two major groups. Ectoparasites live on the surface of the skin of a host. They are invertebrate animals such as ticks, lice, fleas and certain fly species that visit their hosts only to feed. In contrast, the endoparasites, namely roundworms, tapeworms and flukes, live within the organs of the host for their continued existence (Boomker and Horak 2002).
Most Ectoparasites have jointed legs; they usually occur mainly on their hosts, some are parasitic only on their immature stages of development. An example is certain flies of which adults live as non-parasites, while their larvae live in the sinuses, intestines and wounds of their hosts (Boomker and Horak 2002).
Ticks are haematophagous arthropods belonging to the class arachnids (Peter, Van den Bossche, Penzhornand Sharp 2005). Most wild animals found in all regions of South Africa carry varying numbers of ticks. A general rule is that the blue wildebeest and smaller antelope mainly carry ticks in their immature stage, while larger animals such as kudu, giraffe, eland and buffalo carry large numbers of ticks in both their immature and adult stages. A normal healthy blue wildebeest usually carries about 800 ticks, a Burchell´s zebra about 4000 ticks, an impala and kudu about 5000 each and an eland and buffalo between 10 000 and 20 000 ticks each (Boomker and Horak 2002). Ticks have a simple life cycle that can be described as follows. The fully engorged, adult female tick drops from the host and lays her eggs in a protected place. In time, the eggs hatch and the small larvae, sometimes known as pepper ticks, climb onto the grass stems to await the arrival of a suitable host. The larvae then attach themselves onto the host and gorge on its blood. There is a difference between a single-, two- and three-host type of tick (Boomker and Horak 2002): · Single host (blue tick): the larvae moult into nymphs on the host. They engorge and then moult into adults when still on host. The adults mate on the host and the female engorges and drops off. · Two host (red-legged and bont-legged tick):the larvae and nymphs remain on the host, but the engorged nymphs drop from it and moult into adults on the ground. The adult must then attach itself to a second host to be able to complete its life cycle. · Three host (brown ear tick and bont tick): the larvae attach themselves to the first host, engorge, drop off and moult into nymphs on the ground. The nymph must then climb onto the second host, engorge, drop off and moult into an adult on the ground. The adult then climbs onto the third host, engorges and drops off after mating to complete its life cycle. All types of ticks lay their eggs on the ground. Most tick species have certain preferred attachment sites on the host. Ticks generally show a seasonal pattern of occurrence. Most of the larvae occur during the autumn and winter, most of the nymphs during the winter and spring, and most of the adults during the summer. Ticks can harm animal in several ways. They can cause anaemia because of their feeding habits. When large numbers present especially on young animals, the effect can be extremely detrimental. Ticks also reduce the physical condition of an animal and its resistance to disease. Ticks with long mouthparts, such as the bont and bont-legged ticks, cause sores on the skin that may either form abscesses or become infested with maggots, or cause the loss of tail switches, teats and ears. Apart from these direct effects, the ticks are also the carriers of diseases such as corridor disease and heartwater.
It is virtually impossible to control ticks efficiently on wild animals as wild animals cannot be rounded up and dipped like domestic animals. However, when both wild and domestic animals are present on a ranch, the following combined tick control method can be applied with varying degrees of success. During the times when ticks are active, cattle and wild ungulates can be allowed to forage in the same camp so that the cattle can attract as many ticks as possible in a relatively short time. When cattle and wild animals are on the same camps in the autumn and winter, the cattle will become infected with various tick larvae and also with the nymph of two- and three host species. When the cattle are allowed to graze with the wild ungulates in the summer when the adult ticks are active, the ticks will select the cattle, especially when the host antelope on the game ranch are blue wildebeest or small antelope.
The best time to allow cattle to forage with wild ungulates is during January, February, and March, provided that the veld condition allows it. During this time, the cattle should be dipped at maximum intervals of 5 days because longer intervals will allow the adults of some ticks enough time to attach, engorge, and drop off before the cattle are dipped again. The dipped used should have little or no residual effect. The procedure will prevent the maximum number of ticks from climbing onto the cattle during the intervals between consecutive dips. It is essentially to treat all wild animals that are relocated against both ecto- and endoparasites in order to decrease the danger of incidentally translocating parasites to new areas. Wild ungulates can generally be dipped or treated with the same compounds as those used for cattle, provided that the directions for use are followed carefully. Wild ungulates can also be sprayed with an ordinary hand pipe after they had been captured and placed in crates. Spraying should preferably be done when it is hot, and the animals should be allowed to dry off before they are transported. If it is cool or cold, or if the animals are sill wet even on a hot day, they should rather not be transported. A wet animal cools down rapidly in a moving vehicle and this lead to lung infections. Pour-on dips can also be used on wild ungulates. The Duncan applicator has been used successfully for certain types of game. The animals are lured to the apparatus by means of tasty lick. When they are eating from the lick, the neck, head and ears come into contact with a pole down which a pour-on dip runs. This contact is usually sufficient to kill many of the ticks on the animal (Boomker and Horak 2002). Pour-on can be irritating to the skin of young animals (Bester 2004). The step-on applicator is a very effective means of reaching targeted areas where tick species prefer to feed, as nozzles can be adjusted. Doses depend on the weight of the animal and the frequency that the animal crosses the step plate. Animals, especially cautious antelope species, are at first reluctant to step over the device (Bester 2004). Contact applicators are the pole types applicators tend to target tick species around the head and neck area. The animals are lured into the trap with salt lick or feed (pellets). Unfortunately, dominant animals get to eat first. During summer months, when treatment is needed most, the animals, especially young ones, do not take to food that easily (Bester 2004).
Mites are small organisms that are usually only visible under a microscope. They occur on the skin of the ears, legs, feet, shoulders, head and neck, and around the scrotum or udder of large variety of wild animals. Mites are similar to ticks in appearance and cause condition known as mange. Most wild animals are sub-clinically infested with mites. It is only when the animal is subjected to stress or becomes sick that the sub-clinical and signs of mange become apparent. However, usually only individual animals shows signs of mange. To diagnose a mite infestation requires a certain degree of technical knowledge, as skin scraping has to be done and examined (Boomker and Horak 2002). Treatment of mange depends on the species, the pathogenesis and the life cycle of the mite. Sarcoptic mange needs to be treated three times with water-soluble spray at 7 day intervals as the mites live on the burrows in the skin. Injectable solutions may solve the problem but further research is needed. Doses of 1.5 times the normal dose are recommended at 7 to 10 day interval. Psoroptic mange has to be treated twice at a 10 day interval with water soluble spray dip to sufficiently penetrate the tissue fluid scabs that form. Injectable doramectins and ivermectins are also effective at the same interval. Chorioptic mange is usually localised in the perineum area and a thorough once of treatment is necessary. Before considering treatment, the right diagnosis needs to be made. A badly affected animal needs to be immobilised and skin scrapings and biopsies taken. The herds of animals needs to be captured treated and then either released or kept in temporary bomas for follow-up treatments (Boomker and Horak 2002). Lice Lice are relatively small insects without wings. They live permanently on their host and cannot survive for more than a few days away from them. They only occur on specific host and often only on highly specific sites on the host. They are therefore, highly specialised, and host specific. Three main groups are distinguished which are the blue or sucking lice, the red or biting lice and the porcine lice. Lice infestations are not a problem in herds of antelope, but individual animals may have less resistant. Infected animals appear out of sorts, do not eat properly, and tend to stay away from the herd. The only control measure is to capture an animal the infected animals and to deep them individually or to spray them with insecticides (Boomker and Horak 2002).
Fleas are small wingless insects with mouthparts that have become adapted for sucking. They live on the blood of the host and are characteristically laterally flattened. Two main groups of ticks are distinguished: the jumping fleas and the sticktight fleas. Fleas do not become active until stimulated. Flea numbers usually increase during the spring and remain high until autumn. Like lice, fleas usually cause problems on individual animals rather than in a herd, and the same control measures as for lice can be applied (Boomker and Horak 2002).
There are four large groups of internal or endoparasites that are varying importance to wild animals. They are flukes or Tremetoda, the tapeworms or Cestoda, the roundworm or nematode ant the togueworms or Pentastomida. In all four endoparasites, only roundworms will be discussed because they are common in wild ungulates and of all the parasites that occur in wild animals round worms occur in the greatest numbers.
Roundworms occur particularly in the stomach and intestinal canal, but also in the lungs, heart, liver and other organs. Most are small, light brown, red or white worms about 4 to 12 mm long. The life cycle of some of the roundworms is simply. Eggs are excreted with the faeces of the animal, a larvae develops and hatches. It moults twice to reach the infective stage. When there is sufficient moisture in the veld, the infected larvae climbs onto plants. Animals eat the plants and in this way ingest the larvae. The larvae develop in adult worms in the animals abomasum, small or large intestine. Some roundworms use an intermediate host. In such cases, the eggs or larvae of the roundworms are ingested be the intermediate host, usually an insect, and develop into the infective stage. The intermediate host must now be eaten by the final host to complete the roundworm’s life cycle. The host preferences of the worms permit them to be divided into four groups. These are the host-specific group, that is limited to a specific type of animal; the definite parasites that occur in large numbers in most individuals in a herd; the occasional parasites that occur in less half of the individuals in a herd; and the accidental parasites that occur only in individual animals for a limited time (Boomker and Horak 2002). Roundworms are relatively easy to control. A suitable anthelmintic can be mixed into lick blocks that contain fenbendazole and are registered for use in wildlife are commercially available. These blocks or licks should be placed out at several locations on the ranch. The best time to provide these licks is during the winter because the worms spend the winter in their hosts (Boomker and Horak 2002). According to Waller (1987), despite the advent of the broad spectrum anthelmintics, internal parasitism still remains a major limiting factor affecting the productivity of grazing livestock and wildlife throughout the world. The answer to this paradox is quite simply that the outstandingefficiency of these drugs has not generally been matched with any degree of sophistication in their use. This approach to parasite control is becoming untenable, if not because of the high cost of control, which is reason enough, then certainly because of the problem of anthelmintic resistance. It is doubtful that control programme which have anthelmintic treatment as a component can avoid selecting for resistance. However, by careful use of anthelmintics in easily understood, well presented, and properly serviced control programs, should at least be able to delay selection for resistance and so extend the effective field life of these drugs. This will allow more time to explore the possibilities of other methods of control (Waller 1987).
Recommendations for Highlands Wilderness
In order to achieve optimal production, it is essential that the animals on a game ranch remain healthy. Wild ungulates are susceptible to different diseases that reduce their health or even cause death in animals. Ecological studies concerning animal species need to be done thoroughly before introduction in the ranch. Post-mortem examination must be done by a veterinary or a professional to determine causes of death of an animal. A local veterinarian can train the game ranch manager to collect adequate specimens. Post-mortem provides information about internal parasites, external parasites, disease patterns and underlying or potential disease and nutritional deficiencies. The introduction of animals from game ranches where certain diseases occurs should be prevented. If the cause of death is suspected to be anthrax, never open a carcass, it should be burned or call in a veterinarian. Anthrax can also infect humans and can be very fatal. In the rest of the country, African horse sickness (AHS) disease management is by annual vaccination with a polyvalent live vaccine. Holding pens are essential to manage injuries and disease in game species. On Highlands Wilderness Game Ranch, passive capture pens (100 m x 100 m or smaller) ideal to capture antelopes can be constructed for treating and vaccinate animals. Heartwater only occurs in areas where the vector occurs. Springbok, wildebeest, and eland from heart-water free areas are very susceptible. Every animal that is introduced should be checked to avoid newly introduced diseases like heartwater in the game ranch. Tick load is a very serious problem at the moment on Highlands Wilderness Game Ranch as it was experienced during the entire study in the veld. For every 50 metres in the veld, one is covered by very high number of ticks. Introduction of oxpeckers Buphagus species is an effective method of controlling ticks; these birds are associated with cattle and game, and are known to eat hundreds of ticks per day (Sinclair, Hockey and Tarboton 2002). The farm with sable antelope Hippotragus niger and impala Aepyceros melampus had the highest tick count on the vegetation. Selecting for resistant host like blue wildebeest for larval and nymph stages will reduce the burden of adult ticks on sable antelope Hippotragus niger. Wild animals that do not naturally occur in certain habitat should be avoided. Such animals are usually not adapted to survive in new area. They are easily infected with worms and normally carry heavy loads.