Last update: January 14, 2011 10:32:50 AM E-mail Print




J.A. van Rooyen

Grootfontein Agricultural Development Institute, Private Bag X529, Middelburg, EC, 5900

E-mail: Johan van Rooyen 



Biosecurity is defined as:  “The application of management practices that reduce the opportunities for infectious agents to gain access to, or spread within, a food animal production unit” (Thrushfield, 2005).  Sanderson (2009) adds toxins to the definition.  It is also proposed that genetic defects or undesirable heritable characteristics be included in the definition.  A number of plants that do not directly affect the health of farm animals may be introduced with animals or feeds.  Plants that produce seeds that could contaminate wool or hair should also be included in the defined objectives of the practice of biosecurity.  Invader plant seeds, for example Prosopis spp., may also be introduced by animals as live seeds in the faeces (Hoon et al., 1995).  Biosecurity measures could therefore also assist in preventing the introduction of alien plant species.

The following definition of biosecurity, as it pertains to a small ruminant enterprise is therefore proposed:  ‘Biosecurity is the management of all potential biological hazards to production that could be introduced into a flock from an external or internal source.  The objective of biosecurity is the control, prevention or eradication of the potential hazard.’

Extensive as well as intensive small ruminant farmers are not aware of the severe risk that the lack of biosecurity measures on their farms poses to their flock  (Fleming, 2009).  Losses from disease, reproduction failure, poor meat and wool production that could have been prevented by effective biosecurity measures are seen daily by veterinarians in small ruminant practices.  Yet, the implementation of a biosecurity protocol does not require much capital expenses or running costs.



External threats are the potential hazards that are not known to be present on a farm or biosecurity unit of a farm.  A biosecurity unit can be defined as an identifiable geographical or management subsection of the farming enterprise that could be managed in such a way that potential hazards can be prevented from entering and causing production losses.

External threats include invertebrates, infectious agents, unwanted genes and plants.  The hazards are introduced by farm animals, predators and vectors as well as human activity.  Topography, wind and waterways may contribute to the route of access that hazards may follow to gain entrance to a flock.


Internal parasites

Internal parasites are endemic to most small ruminant farms but new species and strains may be introduced if adequate biosecurity measures are not in place.  A few examples are discussed.


Resistant wireworms

The problem of anthelmintic resistance (AR) is well documented (Van Wyk, 2007).  Resistance arises from the repeated exposure of populations of parasites to an active ingredient.  Individual worms that survive the chemical then produce offspring which carry genes that make them resistant.  The way in which stud animals, especially rams are managed, increases the risk of the development of AR.  Stud animals are therefore often accompanied by ‘stud’ parasites.  All purchased animals could potentially be infected by resistant strains of nematodes, with Haemonchus contortus (wireworm) being the most widespread species that shows severe resistance.


Nodular worm

The incidence of Oesophagostomum colombianum (nodular worm) reduced dramatically during the period 1980 to 2000 as a result of the introduction of effective anthelmintics, the relatively low cost of these drugs, and the application of dosing programs.  It was re-introduced into the eastern Karoo and southern Free State from infected flocks from the Northern Cape Province after 2000.


Conical fluke and liver fluke

These parasites were historically largely absent from the north-eastern corner of the Eastern Cape Province.  Over the past 20 years farmers increasingly established permanently irrigated pastures leading to suitable habitats for the intermediate snail hosts.  Cattle farming became more established and cattle were introduced from areas where these flukes are endemic.  The parasite steadily spread from the south, resulting in periodic severe losses in small stock.


External parasites 

Some external parasites are endemic to most small ruminant farms but certain parasites that may be responsible for serious losses, can be eradicated and the flocks maintained free of these parasites.  Maintenance of adequate fencing and buffer zones are essential to the control of parasites that cannot walk or fly onto a farm.  Keeping ticks off a farm is practically impossible and regular chemical control is necessary.  Eradicating parasites on animals that are introduced to the farm will form an essential part of quarantine measures.  A few examples of external parasites that are currently experienced in small ruminant production areas are discussed.


Sheep scab

Psoroptes communis ovis causes widespread serious economic losses especially in wool producing sheep.  The parasite can survive in a tuft of wool attached to a wire fence for up to 7 days.  Infested sheep are pruritic and often rub against a fence, leaving the parasite behind.  Sheep in the neighbouring camp can therefore pick up the parasite across a wire fence.  All sheep, including mutton breeds, should be treated before arrival or upon arrival in a quarantine area on the farm with a product registered for control of Sheep scab.


Itch mite

Psorergates ovis does not cause serious losses but can be a source of constant mild wool loss in infected flocks.  This parasite is introduced through infected animals.



Melophagus ovinus does not cause serious losses but can be a source of constant mild wool loss in infected flocks.  This parasite is introduced through infected animals.


Red Lice

Bovicola ovis (Damalinia) has become a widespread and serious problem over the past decade.  Wool loss may be as serious as in sheep scab.  It is controlled by dipping introductions before or at arrival in a quarantine facility.


Bont ticks

Amblyomma hebraeum transmits Heartwater and is carried by many game species including the warthog.  Warthogs enter farms by burrowing underneath fences and are currently considered the main cause of the spread of Heartwater from the coastal areas, where Heartwater is endemic, into the interior of the Eastern Cape.  Biosecurity measures are currently not successful in preventing the northward spread of Heartwater.


Infectious diseases

Infectious diseases are the main focus of biosecurity practices.  Infectious diseases can be endemic but are often introduced by farm animals or by vectors that gain entrance to the farm.  Diseases that have short incubation periods can often be detected before or at the time of introduction of infected animals and introduction can be successfully prevented.  Diseases that have long incubation periods, present as carriers or persistently infected animals, or become active during mating or late pregnancy, present the greatest threat to biosecurity.  Vector borne diseases, especially when flying insects are involved, are usually not effectively controlled by biosecurity measures.  Intermediate hosts and susceptible endemic mammals harbouring the disease are usually not included in biosecurity measures and many hazards are introduced in this way.


Diseases with a short incubation period  

These diseases can usually be detected soon after arrival and can usually be controlled by placing new introductions in a quarantine facility for two to three weeks.


Table 1.  Selected infectious disease with short incubation periods (Coetzer & Tustin, 2004)


Incubation period


1 to 14 days

Blue Tongue

 7 days (Experimentally 2 to 15 days)

Pasteurella pneumonia and septicemia

Under 7 days


3 to 4 days

Ophthalmia (Moraxella)

3 days to 3 weeks

Ophthalmia (Chlamydophila)

3 days to 3 weeks

Necrotic Balanoposthitis

5 to 6 days


2 to 4 weeks (up to 17 weeks)


7 to 35 days (average 14 days)


2 to 6 days


3 days to 3 weeks


Diseases with a long incubation period.

These diseases may not be detected at the time of purchase or introduction of new animals to a flock.  In practice, when the disease is detected, the infectious agent has already spread to a large proportion of the flock.  Eradication or control then becomes extremely difficult or impossible.  Some of these diseases are presented in Table 2.


Table 2.  Infectious diseases with long incubation periods (Coetzer & Tustin, 2004)


Incubation period

Casous lymphadenitis (Corynebacterium pseudotuberculosis)

25 to 140 days

Ovine Progressive Pneumonia (Maedi-Visna)

Symptoms in 2 to 4 year old animals


5 to 6 months


2.5 to 3.5 years

Johne’s Disease

Animals older than 2 years


2 to 4 weeks (up to 17 weeks)

Footrot and Scab

May be dormant but become active in a later season


Disease that present as carrier states, subclinical or persistently infected animals

Johne’s Disease, Jaagsiekte, Enzootic abortion, Q fever, Brucellosis, A seminis and  possibly Pizzle Disease can be introduced into a flock without the disease being observed clinically at the time of introduction or even weeks after arriving on the farm. 


Diseases that cause abortion

Diseases that cause abortion may only be seen clinically during pregnancy.  It is therefore important to test for these diseases if possible at purchase or introduction on the farm.  Ewes and rams that may introduce these diseases should be kept in separate flocks until the end of the lambing season to make it possible to detect and control these diseases effectively.  Selected diseases that cause abortion are listed in Table 3.


Table 3.  Incubation period of selected infectious diseases that cause abortion (Coetzer & Tustin, 2004).



Toxoplasma gondii abortion

  • 7 – 14 days

Q Fever

  • Months 
  • Becomes active in late pregnancy 
  • Sheds for 8 to 60 days after parturition

Brucella ovis

  • Months. 
  • Becomes active in late pregnancy 
  • Rarely seen

Rift Valley Fever

  • 1 to 3 days

Enzootic abortion (Chlamydophila)

  • Months 
  • Becomes active in late pregnancy 
  • Sheds for 8 to 60 days after parturition

Wesselsbron Disease

  • 1 to 3 days in neonates
  • 5 days before abortion occurs.



Insect-transmitted diseases 

Measures to prevent insect transmitted diseases are seldom successful as most insects travel large distances, especially downwind.  The most common insect transmitted diseases such as Bluetongue, Rift Valley Fever and Wesselsbron Disease can be prevented by vaccination. 

Regular spraying with insecticides to reduce fly and mosquito numbers in intensive enterprises can reduce the risk.  In more intensive systems, flies, nuisance flies and blowfly can be controlled by using baited flytraps.  Mosquitoes, midges and flies in and around buildings can be killed by electrocution, with an ultraviolet light as lure, although this does not contribute significantly to the reduction of the population.

Ectoparisiticides that are registered for the control of insects and nuisance flies may reduce the risk of transmission of diseases.  The incidence of Chlamydophila eye infections can be reduced by applying insecticides to the faces of farm animals. 


Tick-borne disease

Although ticks can walk onto farms, they are mostly introduced on hosts.  Domestic animals can be dipped prior to introduction but feral species may pose a problem.  A disease that is currently creating problems through the introduction of ticks by game animals is Heartwater.  The tick vector, Amblyomma hebraum (bont tick), is found on warthogs, bushpigs and kudu that are migrating northwards into the interior of the Eastern Cape Province.  Fencing to keep the feral species out of farms is currently the only possible control measure.

Intensive systems can be protected from ticks walking onto the property by spraying insecticides around the perimeter, creating barrier areas denuded of vegetation, using fowls to “patrol” this area and even using pheromone treated bait animals to trap ticks.


Transmission by contact

Owing to the flock behaviour of sheep and goats many diseases have adapted to transmission by contact.  It is therefore important from a biosecurity perspective to prevent contact of new introductions or unplanned introductions with the resident flock.  If contact happened by accident the potentially affected flock should be treated as if diseases had been transmitted during the contact.  Appropriate measures should then be taken to isolate, monitor and treat the potentially affected flock.


Venereal transmission

Rams should be kept very secure to avoid accidental contact with the ewe flock before their status regarding venereally transmitted diseases had been established.  Rams are often the cause of a break in biosecurity because of their sexual behaviour patterns.  Fencing for the ram enclosures need to be of a higher standard than that required to contain ewes, lambs and wethers.


Bird-introduced diseases

Many diseases may be introduced into flocks by birds.  Footrot appears on farms in the Karoo regularly just after the first storks arrive from Europe in summer.  As the infectious organism can live in the soil saprophytically, it is possible that the birds are the passive carriers of the disease although this has not been confirmed.  Farmers suspect that Lumpy Wool disease is also introduced by birds, especially cattle egrets who sit on sheep.  Although the birds which actually assist in pest control, cannot be prevented from arriving on the farm, flock managers could consider dipping or foot-dipping flocks in zinc sulphate after the arrival of these two bird species as a precautionary measure.


Genetic problems

Genetic diseases may enter a flock in the form of recessive genes and are often only recognised after the first batch of offspring are born.  It is therefore important to either do a trial mating to establish the presence of genetic defects or to keep an accurate track of the offspring of newly introduced animals that may carry the recessive genes.

Less obvious genetic conditions determining fitness traits such as susceptibility to diseases and parasites,  poor reproduction, mothering ability, and adaptation to the environment, may require a longer term to identify.  Excellent records and identification of animals are therefore essential to manage the introduction of unwanted genetic traits.



Predators do not only kill sheep but can also transmit disease through bite wounds and by acting as intermediate hosts to parasites.  The introduction of rabies on a small stock farm is usually associated with dogs, cats, jackal or mongoose.  Other species may also be involved.  Bite wounds, even minor wounds, from carnivores often present a serious problem and are often unresponsive to treatment.  Lynx are known intermediate hosts for the Karoo paralysis tick (Ixodes rubicundes) and the distribution map of Ixodes and lynx appear to be similiar.  Jackals are known intermediate hosts for Coenerus cerebralis that causes Gid (Draaisiekte) and carry the Taenia multiceps tapeworm.

Control of predators does not imply eradication.  ‘Resident’ jackals may be utilised to occupy their territory.  They can be fed and treated with anthelmintics, endectocides and even contraceptive hormone supplements thereby ensuring control of disease risks and population growth whilst preventing new individuals entering the area.  The newcomers may be adapted to catching sheep and goats and may carry parasites.


Unwanted plants

The Spiny Cockle Bur or Xanthium spinosum (Boetebos) is a well-known plant that produces seeds that attach very strongly to wool.  This seed contaminant may require labour intensive removal from sheep before shearing or, if it is included with the clip, it could lead to a lower price for the wool.  Xanthium strumarium (Large Cockle Bur or Kankerroos) is less common but also a difficult seed to remove from wool.

Jointed prickly pear or Opuntia aurantiaca  (Jointed Cactus or Litjieskaktus) (Henderson & Anderson, 1966) is a common contaminant of mohair and could cause severe matting especially between the back legs of small goats,  leading to restricted movement.  The thorns can inflict very painful puncture wounds to hair handlers and cause financial losses if contaminated hair is presented for sale.   Many species of thistle, grasses and other weeds can be introduced onto a farm attached to livestock.

Animals that are introduced or re-introduced to a farm should be de-contaminated in a quarantine facility and the seeds and plant material carefully destroyed.  Prosopis seeds may be present up to 11 days after ingestion (Hoon et al., 1995).  Faeces should therefore be managed in such a way that seeds are rendered harmless or that emerging seedlings can be eradicated.



Although the primary objective of biosecurity measures is to prevent the introduction or entrance of hazards into a flock, many breeches do occur.  The threat of endemic diseases and parasites can also be reduced by practising internal biosecurity measures in addition to the external measures.

Observations of a flock should be structured with the use of a checklist.  Monthly records of diseases, mortalities and all individual and flock treatments should be kept on file.  A diary of all events that could relate to flock health should be kept.

Animals that are possible sources of infectious agents and parasites should be isolated, treated and/or culled.  Weak and debilitated animals are more prone to infection and can become a source of contamination.

Autopsies should be performed in a secure area and the disposal of hazardous material should be done in such a way that the spread of the disease or parasites is prevented.

Infectious diseases can be spread during handling of animals.  Abscesses should be lanced in an area that can be washed clean with the run-off water being captured in such a way that the bacteria causing the abscess can be killed and not spread by insects or other means.  Needles that are used for administering vaccines, drugs or nutritional supplements, tag applicators, surgical instruments and tattooing equipment often act as mechanical agents for transmitting infectious agents.  An example is an outbreak of Ovine Anaplasmosis that followed tail docking with instruments that were not cleaned between lambs.  Equipment, needles and instruments should be cleaned and disinfected between cases to avoid transmission of diseases.

Hospital camps are a potential source of infection and parasites and should be avoided.  Healthy animals are often kept in hospital camps as a matter of convenience and are then re-introduced to the flock.  Examples are: Newly purchased rams, ewes carrying triplets or more, and animals that have develop fractures or had dystokias.

Parasites on a farm should be managed in such a way that there is no increase that could become a threat and also no genetic change to the parasites that could pose a threat to resident flocks.  The use of anthelmintics and ectoparaciticides should be planned in such a way as to minimise the development of resistance.

Similiar to the measures described to control the introduction of external unwanted genes, the resident gene pool should be managed in such a way that existing unwanted genes do not increase in frequency.

Handling facilities and feedlots should be managed in such a way that there is no build-up of organic material, parasites and infectious agents.  Portable handling pens that are used in different localities are preferred to a fixed structure.  Lambing pens may also present problems in this respect and portable equipment are preferred to enable mechanical removal of contaminated soil and replacement with fresh material.

Predators may contribute to the increased incidence of disease that are present in the flock.  Taenia multiceps/Coenerus cerebralis resulting in Gid (Draaisiekte) is an excellent example.  Resident jackals have been treated successfully with remedies that are effective against tapeworms, thereby removing the source of infection.




The implementation of quarantine procedures is the single most effective way of preventing the introduction of biological hazards into a flock.  The construction of a suitable quarantine station should be one of the first activities of any flock manager to ensure that all animals introduced into the system are managed in such a way that the lowest possible threat to the flock’s health is presented by new introductions.


Quarantine station

Physical terrain.  The quarantine station should be positioned in such a way that animals can be off-loaded into the quarantine facility without any possibility of coming into contact with the resident flock.  The quarantine facility should be adequately fenced and positioned far enough from existing camps, pens or human activity to prevent the spread of hazards. 

Run-off water should not contaminate downstream farming activities.  If no other terrain is available, the run-off water should be channelled into a dam that is inside the qaurantine area. Quarantine facilities should ideally be sited downstream from the rest of the farm.

Insects can pose a serious problem in carrying infective material from a quarantine facility. Quarantine facilities should ideally be situated downwind from the rest of farm.  Quarantine areas should always have their own handling facilities such as races, footbaths and dips.  At least 100 m clearance around animals in quarantine should be allowed to avoid aerosol transmission (Hofmeyr, 2010).


Quarantine procedure

Before purchasing any animals, request a vendor declaration and get a signed committment that sheep can be returned if found to be infected with slow incubation period diseases.


Before departing from source (if possible)

1. Dip all animals.

2. Conduct a Famacha flock examination.

3. Collect a fecal sample from at least 10 animals.

4. Vaccinate the animals as required against at least the following diseases if more than 7 days remain before movement to their destination:


After arrival

  1. Perform a physical examination.
  2. Tag each group with a distinct colour code and record origin and destination.
  3. Clip feet that need attention.
  4. Footbath animals with Zinc sulphate plus small amount of soap.
  5. Dip and inject for external parasites (for example: amitraz plus endectocide).
  6. Collect faeces for fecal egg counts.
  7. Conduct a Famacha flock examination.
  8. Respond to fecal examination results.
  9. Drench if neccessary.
  10. Test the response to drenching after 10 days and act accordingly. (Alternative procedure:  Buy susceptible Haemonchus larvae and drench introductions with low levels to stimulate their immunity.)
  11. Collect blood for serology (discuss with flock health veterinarian – for example: Johne’s disease, Jaagsiekte, Brucellosis).
  12. Respond to serology results: (If any positive Johne’s, Jaagsiekte, Brucella.)
  13. Keep animals in quarantine for at least the incubation period of short incubation infectious diseases. (21 days) or sufficient time for vaccinations to take effect. 
  14. Observe animals daily.  Take temperature and record if possible. 
  15. After release from quarantine facility keep rams seperate untill genital soundness examination and first mating if possible. 
  16. Keep pregnant ewes seperate until after lambing.  Keep ewes seperate until after first mating.  Pizzle Disease becomes apparent only at mating time.

Planned contact with other animals

Group breeding, veld ram projects, shows, sales and shared rams pose a very serious risk to biosecurity of a flock (Van Wyk et al, 1991).  All animals that are re-introduced to a flock should be treated as if that animal was purchased from an unknown source.  Flock managers that take part in these activities should insist on strict biosecurity at these activities and possibly compulsory treatment and testing at admission and again before returning to the flock.


Farm fences

Financial constraints, theft and damage caused by fire, people or animals to fences, all contribute to the reduction of the ability of farm fences to act as an effective biosecurity barrier.  The increase in jackal and lynx predation is leading to a resurgence of ‘jackalproof fencing’.  Electric fences are also increasingly seen.  This trend could improve the biosecurity on farms.

Because of the possible transmission of sheep scab, red lice and other parasites across fences, flock managers are constructing a second fence or additional strands that could keep animals from coming into contact with the perimeter fence.  A single electrified strand at a low level on the inside of the perimeter fence which was intended to prevent jackals from crawling through the fence has had the added benefit of preventing sheep from rubbing against the perimeter fence with obvious biosecurity benefits (personal observation).

Fences should receive top priority as biosecurity measures.  Unwanted stray animals roaming onto the farm could introduce a number of diseases with possible serious financial implications.  Gates are often left open by people that visit by foot and flock managers could consider providing stilus for people to climb over the fence without having to open a gate.  Unplanned visits are however not encouraged because of security risks and even for biosecurity reasons.  Footrot is one example of a disease that could be spread by people.


Shearing teams and other operators, visitors and vehicles

Hired labour, service teams such as shearers and vehicles could be the vehicle for introducing serious disease outbreaks in flocks.  Flock managers should provide their own protective clothing for these operators and also provide showering and laundry facilities for decontamination before flocks are handled.  Shears and other instruments should be disinfected although it is probably advisable that flock managers supply their own.  These measures should even be applied between different subunits or flocks on the same farm.  An example of an outbreak of post shearing Quarter Evil was experienced where 200 pregnant ewes (out of a flock of 2000) died after a team of shearers arrived on a farm from a previous farm where they had slaughtered and consumed a cow that had died of Quarter Evil (Personal observation).  Flock managers regularly report that Caseous Lymphadenitis was introduced by shearing teams.


Contaminated feed

Feed can be contaminated with infectious material especially bacteria that form spores.  Bales can contain tick larvae.  Feed should be carefully examined on arrival and workers should be trained to look out for abnormalities.  It is more advisable to purchase feed from a reliable and regular supplier than to ‘shop around’.  The presence of dead birds or small mammals in feed may lead to Botulism.



Flash floods can wash infective materials onto neighbouring farms.  Faeces that have washed up on river banks or end up in marshy areas may introduce parasite eggs that could lead to parasite outbreaks.  As an example: Lucerne bales, contaminated with Redwater carrying ticks, were washed downstream during the floods of 1976.  This lead to cattle losses along the banks of the Orange River in the Karoo where Redwater does not occur.  Waterways that could introduce infective material should be fenced off to restrict access by animals if possible.  Camps that pose a risk could also be avoided during seasons that pose the greatest threat.


Livestock sources

Flock managers should only buy animals from farms with good biosecurity and general health managament.  To reduce the risk they could rather buy semen or embryos than sires or female animals.  Flock managers should examine animals well before purchase or get a veterinarian to assist them.  Buyers should insist on veterinary health certificates.  The tradition of buying rams on only one farm has largely disappeared and it is no longer possible to assess the risk of introducing diseases, parasites or even genetic problems.  Stud breeders have also become less ‘stable’ in their own biosecurity profile and often use multiple sources of animals in the process of breeding.  Biosecurity risks, as well as general disillusionment with the stud breeding process is leading to an increase in numbers of flock managers who have closed their flocks completely. 


Ensure flock immunity

Endemic diseases as well as epidemic diseases that are insect borne require that the flock’s level of immunity is kept at the required level by vaccination.  However, general immunity needs to be managed equally well by ensuring adequate nutrition, reducing parasite levels that could impact negatively on immunity and even selecting animals with natural immunity and resilience to disease (Gray, 1991; Stear et al, 2007).  Selection for disease resistance can be achieved in most endemic diseases.  Epidemic diseases normally do not offer the opportunity for selection. Animals that are subjected to prolonged stress may suffer from depressed immunity.  Taking care of the welfare of animals will also contribute to a more biosecure flock.


Do a strategic environmental scan to assess risk. 

Farmers and their advisors should include a strategic environmental scan in their management process.  The strategic environment should be scanned for political, economical, social, technological, legal and ecological issues that could impact on biosecurity (PESTLE Scan).  The recent outbreak of Rift Valley Fever (RVF) in South Africa provides a good example.  News reports of outbreaks in countries to the north of South Africa started appearing about two years before the 2010 outbreak.  The outbreak was preceded by at least 3 to 4 months of high rainfall in the areas that could have provided a link to the areas where RVF had occurred.  Cases of RVF were seen in the northern provinces of South Africa the year before.  Although farmers and veterinarians had lost interest in preventing RVF in the 30 years since the previous serious outbreak, a nationally coordinated strategic think-tank could have issued a risk assessment that could have reduced the scale of the outbreak.


Flock records 

The most devastating biosecurity hazards only become apparent months after the introduction of the hazard to a flock.  Flock records are therefore very important to allow a historical trail back to the incident.  The traditional habit of keeping a good diary should be revived and possibly structured to encourage farmers to keep these records. 

All animals or groups of animals that are introduced into a flock should be permanently identified to allow a paper trail at a later stage if cases of a disease with a long incubation periods start appearing.



Farmers need to be informed about the need for biosecurity through organised agriculture, service providers and especially veterinarians.

Livestock agents are the service providers that are most likely to be involved in breaches of biosecurity through farmer to farmer sales, on-farm production sales and, probably the biggest threat, multi-producer sales.  The greatest threats to biosecuriy are, however, posed by the diseases that are inapparent at the time of a sale.  Livestock agents and sellers do not realise the potential threat and consider steps to reduce hazards to be a negative effect on the potential turnover and commission to be earned.  Ways to involve the livestock agents in instituting adequate biosecurty arrangements during livestock transactions should be investigated by producer organisations and veterinary authorities.

A national multidisciplinary strategic think-tank that supports the Livestock Health and Production Group of the South African Veterinary Association’s disease reporting inititative should be established.

An efficient and well-planned biosecurity plan is as important as a herd health plan to ensure sustainable production in sheep and goat flocks.  Veterinarians should focus on the implementation of a flock biosecurity plan as part of the overall strategy to control hazards to production and reproduction.



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Fleming, S., 2009.  Ovine and Caprine respiratory disease: infectious agents, management factors and preventative strategies.  In Anderson, D.E. & Rings, D.M.(Ed.).  Current Veterinary Therapy: Food Animal Practice 5.  Saunders Elsevier.  St. Louis.  Missouri. Page 197.

Gray, D.,  1991.  Breeding for resistance to trichostrongyle nematodes in sheep.  In: Breeding for Disease Resisistance in Farm Animals.  CAB International.  Wallingford.

Henderson, M & Anderson, J.G.,  1966.  Common Weeds in South Africa.  Botanical survey , memoir no 37.  Botanical Research Centre.  Department of Agricultural Technical Services.  Rep. of S.A.

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Sanderson, M.,  2009.  Biosecurity for cow-calf enterpises.  In Anderson, D.E. & Rings, D.M.(Ed.)  Current Veterinary Therapy: Food Animal Practice 5.  Saunders Elsevier.  St. Louis.  Missouri. Pp 595-599.

Stear, M.J., Fitton, L., Innocent, G.I., Murphy, L., Rennie, K. & Matthews, L.,  2007.  The dynamic influence of genetic variation on the susceptibility of sheep to gastrointestinal nematode infection.  J.R. Soc. Interface (2007) 4, 767-776.

Thrushfield, M.,  2005.  Veterinary Epidemiology.  3rd ed.  Blackwell. Oxford.

Van Wyk, J.A.,  2007.  Haemonchus and other gastrointestinal nematodes – understanding anthelmintic resistance in relationship to worm management.  In: Boomker, J.A.  2007  CDRom Helminth Infections of Ruminants. Dept of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria.

Van Wyk, J.A., van Schalkwyk, P.C., Bath, G.F., Gerber, H.M. & Alves, R.M.R.,  1991.  Die gevaar van wye verspreiding van weerstandbiedendheid teen wurmmiddel deur veldramprestasietoetssentra.  Tydskrif van die Suid Afrikaanse Veterinêre Vereniging. 62(4): 171-175.




Grootfontein Agric 11 (1)