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What is African horse sickness?


African horse sickness (AHS) is a highly infectious non-contagious, vector born viral disease affecting all species of Equidae. It is classified as an Orbivirus of the Reoviridae family of which there are 9 serotypes. All serotypes (1-9) are distributed throughout South Africa, although there is a variation in their temporal distribution. It is endemic to (occurs naturally on) the African continent, and is characterised by respiratory and circulatory damage, accompanied by fever and loss of appetite.

Host and Vector


Animals affected are, all breeds of horses (mortality rate of 70-90%), mules and donkeys. Wild life Equine species (Zebras) are resistant to the disease. The vector host, Culicoides midge, spreads AHS virus.

How do horses contract the disease?
AHS does not spread directly from one horse to another, but is transmitted by the Culicoides midge, which becomes infected when feeding on other infected equidae. It occurs mostly in the warm, rainy season when midges are plentiful, and disappears after frost, when the midges die. Most animals become infected in the period associated with sunset and sunrise, when the midges are most active.

Symptoms


The disease manifests in three ways, namely the lung form, the heart form and the mixed form. The lung (dunkop) form is characterised in the following manner:
 

  • very high fever (up to 41 degrees).

  • difficulty in breathing, with mouth open and head hanging down.

  • frothy discharge may pour from the nose.

  • sudden onset of death.

  • very high death rate (90%).


The heart (dikkop) form is characterised in the following manner:
 

  • fever, followed by swelling of the head and eyes.

  • in severe cases, the entire head swells (“dikkop”).

  • loss of ability to swallow and possible colic symptoms may occur.

  • terminal signs include bleeding (of pinpoint size) in the membranes of the mouth and eyes.

  • Slower onset of death, occurring 4 to 8 days after the fever has started.

  • Lower death rate (50%).


The mixed form is characterised by symptoms of both the dunkop and dikkop forms of the disease.

Diagnosis and Notification


The symptoms described above may assist with an initial diagnosis of AHS. This diagnosis can only be confirmed by identifying the virus in a laboratory. It is, therefore, essential that blood samples be taken from the horse during the fever stage of the disease for analysis. As AHS is a controlled disease, horse owners are obliged by law to notify the local State Veterinarian of suspected cases.

Note: Excerpts taken from Onderstepoort Biological Products leaflet.
 

Control of African Horse Sickness

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African Horse Sickness (AHS) is one of a number of diseases known to be potentially damaging to the livestock economy. By way of the Animal Diseases Act (Act No. 35 of 1984), AHS has been declared a state controlled disease, thereby empowering the state to implement measures to control the disease. Horse owners are also required by this law to notify their local state veterinarian of any cases of AHS. The Act also requires that all equines (horses, donkeys and mules) must be vaccinated at least once a year with an approved AHS vaccine.
 


Movement controls into the AHS Control Area in the Western Cape were introduced when the export protocol (1997/10/EC) was ratified by the European Commission in 1997. Based on guidelines given by the World Animal Health Organisation (OIE), and South African and European legislation, the South African Veterinary Authority established a policy for the movement of all equines into this area.
 

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39.1 AFRICAN HORSE SICKNESS

39.1.1 All HORSES and all FOALS shall be vaccinated against African Horse Sickness by a veterinary surgeon, using a registered, non-expired vaccine according to the manufacturer’s recommendations, in accordance with the programme of vaccination as published from time to time in the RACING CALENDAR. Such vaccine shall be supplied by the Veterinarian administering the vaccine.

39.2 The OWNER, the TRAINER and/or any other PERSON responsible for the care, treatment or training of a HORSE which is required to be vaccinated in accordance with RULE 39.1 shall be individually and jointly responsible for ensuring that such HORSE is so vaccinated.

39.3 The OWNER, the TRAINER and/or any other PERSON responsible for the care, treatment or training of a HORSE which is required to be vaccinated in terms of RULE 39.1 shall be guilty of an offence if such HORSE is not vaccinated as prescribed.

AFRICAN HORSE SICKNESS VACCINATION PROGRAMME

1. Acting in Terms of Rule 39.1.1., the NATIONAL BOARD has issued the following directive in respect of the compulsory vaccination of HORSES:

2. All HORSES, except those referred to in 7. below, and those resident in Zimbabwe and the area defined in 3. below, shall be vaccinated against African Horse Sickness by a Veterinarian, using a registered, non-expired, polyvalent horse sickness vaccine according to the manufacturers’ recommendations :-

2.1 two sets of vaccines as FOALS between the ages of 6 and 18 months, not less than 30 days apart and, where possible, between 1 June and 31 October, and thereafter

2.2 every year between 1 June and 31 October.

3. No HORSE resident in the magisterial districts of Cape Town, Vredenburg, Hopefield, Moorreesburg, Malmesbury, Wellington, Paarl, Stellenbosch, Kuilsrivier, Goodwood, Wynberg, Bellville, Simonstown, Somerset West, Mitchells Plain and Strand, shall be vaccinated against African Horse Sickness unless written permission of the Director of Animal Health of the Republic of South Africa has been obtained.

4. Any HORSE, except those referred to in 7. below, moving from the area described in 3. above, to the rest of the country between 1 November and 1 May, which has not been vaccinated in terms of 2.2 above, shall be vaccinated as instructed in writing by a Veterinarian employed by the NATIONAL HORSERACING AUTHORITY.

5. HORSES resident in Zimbabwe shall be vaccinated against African Horse Sickness by a PERSON or a Veterinarian using a non-expired, registered, polyvalent horse sickness vaccine according to the schedule prescribed in 2.1 and 2.2 above.

6. All HORSES and FOALS resident in the magisterial districts of Clanwilliam, Piketberg, Ceres, Tulbach, Worcester, Caledon, Hermanus, Bredasdorp, Robertson, Montagu and Swellendam shall only be vaccinated between 1 June and 31 October.

7. All registered stallions and mares, standing on stud farms, except those referred to in 3. above, shall be vaccinated against African Horse Sickness by a Veterinarian, using a registered, non-expired, polyvalent horse sickness vaccine according to the manufacturers’ recommendations, at least once every calendar year and where possible, between 1 June and 31 October.
(Amended 29.05.2015.)

Rule 39.2 and 39.3 also applies to influenza vaccinations.

PROTOCOL FOR THE AHS VACCINATION OF HORSES MOVING OUT OF THE AHS SURVEILLANCE AND FREE ZONES

NHA AHS vaccine requirements for horses moving out of the AHS surveillance and free zones.

1. The overriding principle is that according to NHA rules, horses racing outside of the AHS surveillance and free zones must have a valid AHS I and II vaccine, administered between 01 June and 31 October, in order to compete.

2. This implies that “raiders” must be properly vaccinated with official permission from the State Vet to vaccinate, BEFORE they leave the surveillance or free zone. Any horse that a trainer feels may be sent to race elsewhere in the country, should be vaccinated in the June to October period, as is done in the rest of the country. The State is not going to permit vaccination of these horses in the November to May period, except under exceptional circumstances and with strict quarantine and monitoring. Such a vaccine would then be considered valid for one year.

3. In the case of unvaccinated horses moving to the rest of the country as a permanent transfer or to race for a season (i.e. not to “raid” for a specific race), they must be vaccinated within a week of arrival, with the second vaccine administered 21 days later. The horse may NOT race until it has received both vaccinations. Should these vaccinations fall within the November to May period, the horse would then need to be revaccinated again that same year between June and October, in order to comply with the NHA rules.

4. There is however a principle that has been in place throughout the country, where a horse presented to race with a vaccine discrepancy, is permitted to race that day, but may not compete again until that discrepancy has been rectified. It would therefore be fair to allow a horse from the surveillance/free zone that has been vaccinated within the last 24 months, to leave the surveillance/free zone, compete in one race and return to the surveillance/free zone without having to be revaccinated. However, the assumption is that the horse fulfils ALL State requirements pertaining to moving back into the surveillance/free zone. This would only be allowed once. A horse may not move backwards and forwards between Port Elizabeth and Cape Town on a regular basis for example, without being vaccinated annually.

5. Likewise, a horse moving permanently to the rest of the country or to race for a season, would be allowed one race within the first week “unvaccinated”, but then the provisions of point 3 above would apply.

6. It is impossible to address every potential scenario in one document, so any queries in this regard MUST be referred to the NHA veterinarians, who will advise you in writing on how to vaccinate. To avoid unnecessary conflict, this should, where possible, take place PRIOR to any horse moving out of the surveillance/free zone.

An African Horse Sickness control policy has been created by the Western Cape government to control the movement of horses within the AHS Controlled Area. The regulations regarding the requirements to move horses, boundaries of the zones, entry/exit points between the zones, and a map of the zones can be found on the website: http://www.elsenburg.com/. The website also contains the information on current movement bans, and lifting of the movement bans.

AHS (African Horse sickness) Movement control:
The AHS movement control of horses across South Africa is subject to the regulations of the Department of Agriculture. The Director Veterinary Services, Western Cape recently issued a movement notice that is available to download. (Download Here)

By following the links provided, trainers and owners can educate themselves the protocols.

The current provincial requirements to move into the controlled area:
http://www.elsenburg.com/sites/default/files/attachments/2016-10-17/AHS-CONTROL-BROCHURE-Upd2016.10.pdf

For movements during high risk periods for AHS:
http://www.elsenburg.com/sites/default/files/news/african%20horse%20sickenss/AHS%20Stop%20Over%20Quarantine%20Protocol%202017.pdf

Summarised schematics:
http://www.myhorse.org.za/infographics/basicmove.pdf
http://myhorse.org.za/infographics/movepztosz.pdf

African Horse Sickness Vaccination Guidelines

(as on NHA)

Protective Measures


Apart from vaccination, horse owners should consider the following additional measures to reduce exposure to the disease:

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  • Stable horses when the vector is most active i.e. from late afternoon to mid morning. Recommended 9:00am (or when the grass dries) - 15:30pm

  • Cover all access points in the stable with 80% shade cloth – it has been proven to reduce the midge activity inside the stables up to 14 times. For horses living out, shade cloth awnings could be built and horses enclosed during the night.

  • Place fans in stables 

  • Midges are attracted to horse odors and the carbon dioxide emission of the horses – a fan will assist in dispersing the odor trail.

  • Midges are very light and appropriately directed air movement makes it difficult for them to enter stables and/or to stay immobile long enough to feed.

  • Automatic insect repellents like Mortein attached to stable wall

  • Applying insect repellents like Tabbard, etc (may assist in reducing the number of midges feeding, but is not guaranteed or necessarily adequate to protect animals completely)


The spread of the disease is directly linked to the midge activity in the area and this is dependant of a number of conditions, rainfall, and temperature and soil types. Areas that have sandy soils seem to have less midge activity as areas with clay based soils. The high rainfall we have been experiencing increases the breeding cycle of the vector and therefore increases the transmission of the disease.

Myths

  • Smoking drums at stables – this seems to have no effect on midge activity

  • Garlic supplements – no scientific evidence that supports this.

  • Moving horses to higher ground – depending on other factors, midges can operate at altitude.

  • Previously vaccinated horses can be worked normally during the vaccination period only if no febrile reaction to the vaccine is indicated. Horses receiving their first AHS vaccine should not be exercised or only minimally exercised during the 6-week vaccination period.

More ways of protecting your horse from horse sickness and other viral diseases.

(by Laura Seegers)

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We are all familiar with the standard advice on keeping your horse safe from African Horse Sickness:

 

vaccinate annually, stable your horse from late afternoon to well after sunrise,

apply insect repellents daily. However, these precautions have sometimes failed to prevent a horse coming down with horse sickness, with serious results.

For those horse owners who do all these but want to do more, and for those who do not have stables and whose horses run extensively and are not handled daily, I want to offer more options in the interest of keeping our horses alive and healthy.

Help nature’s predators control the vector insects.

Viral diseases go hand in hand with good rains and lots of midges and mosquitoes. You can help restore natural checks and balances, by encouraging frogs in natural puddles, fish in dams and rivers and troughs, and bats around the yard. People love to spray insects with poison, but this not only knocks the target species but their natural predators as well, with the result that the unwanted ones return in greater numbers than before. Take long term view throughout the year and build bat boxes near your horses. There are designs on the internet and if you build a secure home then bats will move in on their own. One bat can eat 2000 insects in a night. Mosquito fish in troughs will eat mosquito larva which can carry West Nile Virus. Banded tilapia are a small indigenous fish that are also suitable for reservoirs and dams. Frogs are very good at insect control, but very sensitive to pesticides. Look after your predators. By reducing the bloodsucking insect burden you will help your horses immensely. Nature never works by eradicating anything entirely, but by balancing populations.

Unburden your horse internally.

Intestinal worms are another population that explodes when good rains fall. I have been unsuccessful in finding an effective natural worm control that works on encysted worms. I am sure there is a natural product that will do this, I just haven’t found it. Most regular worm doses don’t work on them either. The very best advice I can give is the 5-day Panacur protocol. Dose your horse once daily and repeat for five consecutive days. (I would use 30-40ml daily for an adult horse depending on size, 10-20ml for a foals of different ages. Check with your vet.) This will clear out the adult worms plus the encysted ones in the intestinal wall. We do this with all our horses twice a year. Horses that are not thriving can get an extra course. Worms are implicated in lowering immunity to sickness. Whether this is purely as a result of draining nutrients from the horse or something more complex, I don’t know.

Bantam hens help control manure piles.

Fresh manure provides a breeding ground for flies, worm larva, bots and midges. A flock of hens or guinea fowl with access to the yard and fields the horses run in can work wonders by reducing problem insects. They scratch open manure piles straight away. They will break the botfly cycle by eating bot larva before they can mature into flies. The fowls open up the dung to the drying effect of the sun and this will make it less attractive to the type of midge that hatches in manure. They also peck up ticks from the grass before they climb onto the horses.

Make sure your horse has all the minerals.

Mineral nutrition deficiencies can exist even when horses look good. Mammals need just about every mineral we find in seawater, and most never get the full spectrum, because soils are washed out. Just because we don’t know what each one is used for, doesn’t mean we don’t need it. They can survive without a lot of the trace elements, but they will not experience every benefit they could. If you can, give your horse a cup of seawater every day. It will love it on feed or in drinking water. In large scale operations it can be added to concrete reservoirs that fill drinking troughs. Himalayan rock salt has the second most minerals. The pink salt licks can be bought at tack shops or more cheaply from the wholesalers. General mineral blocks have far fewer minerals, and in my private opinion way too much manganese and iron, but they may be better than nothing at all if your district is very deficient in trace elements. Immune function specifically needs Vit A, Vit E, zinc, copper and selenium. Pay particular attention to supplementing selenium. Selenium deficiency has been shown to be linked to an increased vulnerability to viral diseases and also the virulence of the outbreak. Even mainstream orthodox science has noticed this. The selenium status of your horse might make the difference between it getting horse sickness or not. It might make the difference between a mild case or a fatal one. Most of South Africa’s soils are deficient in selenium and our animals are probably chronically deficient. I recommend Stride SeeVitE liquid supplement for your horses as the safest and most bio-available form I know. If you have pastures they can be fertilised with selenium salts. The Natal dairy farmers I know supplement their cows. For general pasture health the Albrecht method of soil balancing must be the best route to take. John Fair’s www.sabiofarm.co.za can advise on that.

Any one of these precautions alone is not enough to prevent horse sickness or other insect borne diseases. But together they have a powerful synergistic effect that will contribute to the overall well-being and resilience of your horse.

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