• Insect Transmitted Disease of Horses

    Posted by Tack 'n Togs Midfeeds

    When we discuss insect transmitted diseases the first one that comes to mind is African horse sickness which is viral in nature and transmitted by biting midges or culicoides. Although we widely advise vaccination it is not a guarantee that your horse will not possibly contract the disease. The recommendation from various sources are to prevent bites from midges, as once they have bitten infection has possibly already occurred.


    This is also relevant when we think of West Nile disease that is transmitted by mosquitos. West Nile positive horses 2006-2016


    And then we have the sheer irritant factor when we consider flies. So how do we choose the most effective insect repellent on the market, from the multitude available? In order to make an informed choice it is important to consider the active ingredient in your choice of insect repellent spray.


    Deet (N,N-diethyl-3-methylbenzamide)



    DEET was developed in 1944 by Samuel Gertler (Gertler, 1946)of the United States Department of Agriculture for use by the United States Army, following its experience of jungle warfare during World War II. It was originally tested as a pesticide on farm fields, and entered military use in 1946 and civilian use in 1957. It was used in Vietnam and Southeast Asia as an insect repellent to combat malaria and other insect transmitted disease.

    Uses & efficacy

    In a 2002 study it was found that DEET was up to 95 % effective as a mosquito repellent for more than 5 hours. (Donald R. Barnard, 2002), (H.H. Yap, 2000) (Mark S. Fradin, 2002) (S.P. Frances, 1998) During a study in 2005 it was proven that DEET is as effective in pyrethroid resistant mosquitos as in normal populations. (CEDRIC PENNETIER, 2005) Various studies done around the world on Cullocoides have found that DEET based insect repellants were up to 97 % effective up to 8 hours after application. (C.E. Schreck, 1981) (C.E.Schreck, 1979). In a 2005 study DEET was compared to Citronella and Cypemethrin under local conditions, it was found that Deet was most effective with Citronella having no effect and cypemethrin only being mildly effective. (P.C. Page, 2009)

    DEET has even been proven to repel stable flies,and ticks.


    DEET has a remarkable safety profile after 40 years of use and nearly 8 billion human applications. When applied with common sense, DEET-based repellents can be expected to provide a safe as well as long-lasting repellent effect. Despite the substantial attention paid by the lay press every year to the safety of DEET, this repellent has been subjected to more scientific and toxicological scrutiny than any other repellent substance. (Mark S. Fradin, 2002).

    From the research available locally as well as internationally it is clear that it is of upmost importance to select the most effective active ingredient when selecting an insect repellent spray. When combined with management procedures, this provides the best opportunity to combat possible infections of African Horse sickness and West Nile Virus.

    IR3535 (Ethyl butylacetylaminopropionate)


    Developed by Merck in 1970. It was created by mimicking the molecular structure of compounds with known repellent properties. The chemical structure of IR3535 is based upon β-alanine, a naturally occurring beta amino acid.

    Efficacy and use IR3535 is a broad spectrum repellent. It repels a variety of biting arthropods including mosquitoes, flies, chiggers, midges, fleas, body lice and ticks (Carroll, 2008). Unlike DEET, IR3535 has also been shown to be effective against head lice, bees and wasps.

    As it is solely a repellent it has no killing action and does not give rise to selection pressure or development of resistance. It is biodegradable and completely degraded in the environment within a very short time. (Donald R. Barnard, 2002)

    Lemon Eucalyptus

    In a 2006 Study lemon eucalyptus–based repellent was tested against the biting midge Leptoconops carteri Hoffman in the Central Valley of California. This relatively new active ingredient has demonstrated high efficacy in a number of studies with mosquitoes. It also proved to be relatively effective in this study.. (Scott P. Carroll, 2006)


    C.E. Schreck, D. K. (1981). Repellency determinations of four commercial products agians six species of biting midges (Diptera: Cullicoides). Mosq News. C.E.Schreck, N. T. (1979). Repellency of selected compounds against two species of biting midges (Diptera: Ceratopogonidae). Journal of Medical Entomology. Carroll, S. (2008). Prolonged efficacy of IR3535 repellents against mosquitoes and blacklegged ticks in North America. Journal of medical entomology. CEDRIC PENNETIER, V. C.-M. (2005). COMBINATION OF A NON-PYRETHROID INSECTICIDE AND A REPELLENT: A NEW APPROACH FOR CONTROLLING KNOCKDOWN-RESISTANT MOSQUITOES. The American Journal of Tropical Medicine and Hygiene, 72(6), p. 739 - 744. Retrieved from https://doi.org/10.4269/ajtmh.2005.72.739 Donald R. Barnard, U. R.-D. (2002). Repellency of IR3535, KBR3023, para-menthane-3,8-diol, and Deet to Black Salt Marsh Mosquitoes (Diptera: Culicidae) in the Everglades National Park. Journal of Medical Entomology, Volume 39, (Issue 6), Pages 895–899. Retrieved from https://doi.org/10.1603/0022-2585-39.6.895 Gertler, S. (1946, 10 1). a b US 2408389, Gertler, Samuel, "N,N-diethylbenzamide as an insect repellent", published 1946-10-01. H.H. Yap, K. J. (2000). Field efficacy of four insect repellent products against vector mosquitoes in a tropical environment. J. Am. Mosq Control Assoc. Mark S. Fradin, M. a. (2002). Comparative Efficacy of Insect Repellents Against Mosquitoes. New England Journal of Medicine. Retrieved from http://www.nejm.org/doi/pdf/10.1056/NEJMoa011699 P.C. Page, ,. K. (2009). Duration of repellency of N,N-diethyl-3-methylbenzamide, citronella oil and cypermethrin against Culicoides species when applied to polyester mesh. Veterinary Parasitology, 105-109. Retrieved from https://doi.org/10.1016/j.vetpar.2009.03.055 S.P. Frances, R. C. (1998). Laboratory and field evaluation of the repellents DEET, CIC-4 and AI3-37220 against Anopheles farauti (Diptera: Culicidae) in Australia. Journal of medical Entomology. Scott P. Carroll, J. L. (2006). Field Test of a Lemon Eucalyptus Repellent against Leptoconops Biting Midges. The American Mosquito Control Association, Inc. Retrieved from https://doi.org/10.2987/8756-971X(2006)22[483:FTOALE]2.0.CO;2