Autumn is coming and the usual symptoms of chill also manifest in horses: increase in body temperature, cough, mucus, apathy and reluctance to engage in physical activity.
This is not surprising inasmuch as equine influenza is the most common respiratory viral pathology in horses.
Present in almost all the world, equine influenza is very contagious and generally affects immunocompromised horses, that is to say those who have not received immunity through vaccination, or those who have a weak immune system mainly due to prior infections.
In the early 80’s, after a serious epidemic occurred in 1979, the annual vaccination of horses became compulsory in many countries. In some countries, it even became compulsory every six months. Needless to say, the spreading of major sources of equine influenza has significantly decreased since the introduction of the compulsory vaccination.
We said first that equine influenza was present all around the world. There are some exceptions, among which are Iceland, New Zealand and Australia. In 2007, in Australia, because of a serious deficiency in the implementation of quarantine, the virus spread and created a serious epidemic that was only stemmed a long time afterwards, thanks to important prophylactic measures. In Iceland, since 1909, it has been forbidden to import horses: this aims to protect and save the Icelandic breed, as well as to prevent a new contamination and a spread of equine influenza sources. Also in New Zealand, thanks to drastic security measures, no important source of equine influenza has ever been observed.
The causes of influenza in horses
Equine influenza is caused by an RNA virus named orthomyxovirus type A influenza, itself subdivided into several serological subtypes. The subtypes currently known are very numerous, but only two of them have been identified as pathogenic for horses: H3N8 and H7N7. Since 1979, H3N8 virus has caused all epidemics, so we can consider H7N7 currently inoperative.
It has been calculated that, during an epidemic such as the ones that occurred in the past, each horse affected by influenza can transmit it to ten other horses.
Equine influenza spreads through the respiratory tracts, mainly by direct contact between infected horses and immunocompromised horses. It can also spread by air when the conditions are particularly favourable: immobilization in a little-ventilated or unhealthy place, or in high overcrowding conditions.
Symptoms of equine influenza
The most common clinical features are:
- nasal flow
- purulent mucus
- depression of sensory organs
- lack of appetite
- myalgia or muscle pain
- swollen submandibular lymph nodes, in the most serious cases.
The clinical features are generally less serious and less flagrant in vaccinated horses or in partially immune horses. They can include a dry cough and low or light athletic performances, a very unfortunate event for sport horses.
Other features may be added to these clinical features, such as: viral problems on the ciliary respiratory epithelium, temporary loss of the mucociliary clearance process, higher sensitivity to bacterial infections and allergens.
The infection is rarely fatal, but the complications due to secondary infections (such as pneumonia and pleurisy) can lead to the death of some subjects who have a very weak immune system.
Normally, the infection is immunogenic, that is to say that it creates an immune response, and it is generally overcome 7 to 10 days later. Some clinical features such as cough may need more time to resorb because the ciliary respiratory epithelium must be re-stabilised. Horses are generally immune against new infections for a long time after clinical features have disappeared.
Diagnosis of equine influenza
Initially, the diagnosis of equine influenza is based on the typical clinical features, but the definitive diagnosis rests on the results of laboratory tests, among which is the identification of the virus from samples taken from the respiratory tracts.
Nasopharyngeal swabs must be taken and subjected to an enzymatic test named ELISA in order to detect the virus nucleoprotein.
Concerning the hematologic profile, we can note anemia, leukopenia (decrease in the number of leukocytes), and lymphopenia (decrease in the number of lymphocytes).
The horses affected by equine influenza must immediately be isolated. The first requirement is a complete rest in a very well ventilated box.
Obviously, the most efficient treatment remains prevention. An appropriate vaccination program, every six months or every year, allows to reduce the risk of viral or secondary bacterial infections.
In case of secondary bacterial infections, treatment includes the use of specific antibiotics, or of antiallergics in cases of infections due to allergens. In both cases, they are combined with antibiotics and anti-inflammatory drugs to neutralize the risks generated by a high temperature.
In sport horses, it can be helpful to use interferons in spray form on occasion, at a rate of 5-6000 u.i. of interferon alfa in spray form for 7 to maximum 10 days, to repeat twice or three times per year.
Natural medicine advice
Prevention of infection and boosting of the immune system are the main modes of action of ozone therapy.
In effect, ozone is an extremely powerful antiviral molecule. Its action, firstly on the increase of leukocytosis, that is to say on the increase of white blood cells, and secondly on the development of the phagocytosis, is scientifically proven.
The antiviral activity of ozone comes from the capacity of this molecule to interfere with viruses through their outer layer and to act on the viral receptors by causing an alteration of their electronic configuration. Then the virus becomes unable to enter the target cell, which consequently blocks the replication cycle.
OzoneForce, ozonated sunflower seed oil with a high concentration of peroxides, administered orally in doses of 10 ml. per day, is an indispensable ally in natural alternative therapy to fight against clinical and subclinical viral infections.
Its proven efficiency is heightened by its own specificity, which is its ability to act very quickly by neutralizing the viral action as soon as the first symptoms appear and without any contraindications, or even rather with a desirable side effect consisting in renewed energy and wellness.
Barquero N, Daly JM, Newton JR. Risk factors for influenza infection in vaccinated racehorses: lessons from an outbreak in Newmarket, UK in 2003-2007
Callinan I. Equine influenza: the August 2007 outbreak in Australia. [Report of the equine influenza inquiry, Commonwealth of Australia] 2008.
Yamanaka T, Tsujimura K, Kondo T, et al. Evaluation of antigen detection kits for diagnosis of equine influenza.J Vet Med Sci. 2008;70:189–192.