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Posted on June 20, 2013
In The Saddle specialise in riding holidays throughout the world and was initially founded on a passion for horses and travel. The health and welfare of the horses on our rides is of utmost importance to us. In this blog, Louise Carelsen of Limpopo Valley Horse Safaris talks about their struggles with African horse sickness (AHS), a highly infectious non-contagious, viral disease endemic to the African continent,affecting all species of Equidae.
What is African Horse Sickness?
African horse sickness is one of the most agonising sicknesses a horse can get and having lived in Botswana for almost 10 years, we have been unfortunate to witness several cases ourselves. The virus is classified as an Orbivirus of the Reoviridae family of which there are 9 serotypes.
My personal experience of this virus started when I was a volunteer at Equus horse safaris in 1998 where my boss Wendy Adams told me about this terrible virus and what to look for; a high fever and big puffy head especially in the hollow above the eyes where the most obvious things. While I was there one of the horses did indeed get the mild non dangerous form of it and I remember vividly as everyone monitored him carefully and treated him symptomatically. I also remember how we had to vaccinate all 30 horses 2 doses 3 weeks apart as it’s a live attenuated vaccine we had to keep it cool all the way from the vet to us, inject it as quickly as possible sub-cutaneous and then rest the horse during the middle week after each vaccine.
Tackling the virus ourselves
In 2003 when my husband and I moved to Mashatu as part of Limpopo Valley Horse Safaris I was to become further acquainted with this dreaded virus. 2003 was a particularly rainy year and as the virus is transmitted by a tiny midge, either Culicoides imicola or C. bolitinos (you can fit 10 on the head of a match that’s how small it is) which is active in wet/humid areas we soon had a stable full of fevers. Most of what we were seeing was something our vet calls ‘African Horse Sickness Fever’ usually presenting as just a medium to high temperature for a few days, treated with Finadyne (Flunixin) or Phenylbutazone. Occasionally, fevers may also have been due to another virus called Equine Encephalosis which is caused by an orbivirus related to AHSV, and again spread mainly by the culicoides midge. Encephalosis can only be diagnosed by taking blood which is a luxury we simply don’t have in the bush. Although it has a less than 5% mortality rate, it unfortunately lowers the resistance of the horse to other viruses like AHS. Typically, the horse presents with signs of depression and listlessness but is usually eating with a fluctuating fever. After a week or two, it seems like the horses is recovering but often there will be a sudden relapse… the horse gets sick again but this time it’s with full blown AHS.
AHS can present as either the pulmonary form (known locally as din kopp), in which case we often don’t see very many obvious symptoms except for increased heart and respiratory rates, fever and nasal discharge. Horses usually keep eating until they are very distressed. The second form is the Cardiac form (dick kopp) with more obvious symptoms, characteristically, the big puffy head, (sometimes) prolapses of the eyes and filling up of the inter-mandibular space. The horses’ nasal passages are restricted so they have trouble breathing. Horses can also be infected with a combination of the above two types, the disease then shows itself initially by mild respiratory signs followed by the typical swellings of the cardiac form. Usually the Pulmonary form has about a 90% mortality rate and the Cardiac form about 50%.
Treating the virus
The treatment we have used here in Botswana has evolved over the years and our vet, (based 5 hours away in Johannesburg – S.Africa) is always very generous with her time and advice to us. Symptomatic treatments we use include non-steroidal, anti-inflammatory drug – Finadyne (Flunixin), for the pain and fever (up to 2 or 3 doses per 24 hours) and penicillin for secondary infections/complications. In more extreme cases or when the heart rate goes above 70 or 80 bpm we will put up a drip and begin fluid therapy. We administer Colloids or Voluven at a rate of 1 to 3 litres for every 3 litre of Ringer’s Lactate or Sabax. We would also give Calcium Borogluconate (20ml per 100kg of body weight) in the Ringer’s Lactate as there has been some research to show that this may be beneficial. I have also once given DMSO (dimethyl sulfoxide) in the drip when we had a horse with a heart rate that kept going up, this helped to keep the horses heart rate below 90bpm and the horse survived. More recently we have used cortisone (dexamethasone) effectively for horses where we thought it was getting to a crucial stage. The use of corticoid steroids is a bit controversial as they do not allow the horse to build up immunity to the virus should the horse become infected again. But all these treatments are merely supporting the horse in his own endeavours to overcome the virus.
On average we have lost one horse per year since we have been living in Botswana, recently less which may be due to the fact that our vector control is better as we have fans installed for the horses in the stables or just that it’s been less rainy. Despite preventative measures, every year between February and June we still get up to 10 horses with what we presume is the Horse Sickness Fever form of AHS. This is quite difficult to manage too as the horses are supposed to have 1 week off for every day of high temperatures and as the horses can sometimes have a temperature for up to a week it doesn’t make it easy to manage safaris!
Some of the local Botswanan farmers still have some very weird ideas to either prevent or treat AHS, including giving the two dose vaccine in one go – one batch on either side of the neck! Or treating the horses with Formalin (an aqueous solution of the chemical compound formaldehyde) by IV injection or giving the horses mega doses of medicines all at the same time so the horse either falls down dead or survives?! Some farmers swear by giving the horses Dagga (Marijuana) to eat when they are sick. Prevention traditionally has been to put paraffin on the horses and some will burn old hay around the stables in an attempt to smoke out the midges. Neither of these old fashioned methods has been proven to work in protecting the horses. What does work is stabling the horses during dawn and dusk when midge activity is at its highest, as well as using cypermethrin based insect repellents or DEET based insect repellents. Careful monitoring is also vital! We take the horses temperatures twice a day from Feb through to June.
Ongoing research is proving essential in improving the recognition, prevention and management of this virus. With the ever increasing risk of spread of AHS into Europe and the UK, it is vital that horse owners globally are educated. To find out more about In The Saddle’s commitment to the health and welfare of the horses on their riding holidays visit www.inthesaddle.com