Effect of gender on horse allergies is not well understood – review

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More research is needed into how gender differences affect allergies in horses, a scientific review has concluded.

The Austrian review team found that little is known about atopic dermatitis (eczema) in horses, and even less about how gender affected it. Atopy refers to the genetic tendency to develop allergic diseases. It is typically linked to heightened immune responses to common allergens, which may be inhaled or eaten.

“The main symptom seems to be itching and clinical symptoms appear seasonally or throughout the year,” researchers Ina Herrmann, Lukas Einhorn and Lucia Panakova wrote in the World Allergy Organization Journal.

Currently, only food, insect and environmental allergies were linked to allergy-related skin problems in horses in veterinary dermatology.

Allergies were also behind some respiratory tract issues in horses, believed to be caused by inhaled molds, which showed similarities to certain forms of asthma in humans, they noted.

“As equine atopic dermatitis has rarely been described in clinical studies, only little is known about the gender influence,” the review team, from the University of Veterinary Medicine, Vienna, said.

In one retrospective study on atopic dermatitis in horses involving 54 animals, male horses (predominantly geldings) were over-represented in contrast to their female counterparts (35 to 19). However, this was statistically insignificant compared to gender distribution in the clinical study population.

In a recently published study on insect bite hypersensitivity in the Old Grey Kladruber horse, information on 1209 studbook horses was recorded and analyzed over 13 years. There was a smaller risk of affliction in the stallions than in the mares and this difference was statistically significant.

In a study on summer eczema in 490 Icelandic horses from 24 stud farms, mares (33.1%) and geldings (29.1%) were more often affected than stallions (15.5%).

Another retrospective case-control study investigated 1444 horses with recurrent airway obstruction (RAO) and 1444 control horses examined for other reasons.

The risk of the ailment in females was 1.4 times higher than in sexually intact males, and females were more likely to be examined for the condition than entires.

On the contrary, earlier studies did not identify sex differences as regards susceptibility to the condition.

“The biological explanation for this difference is unclear, but it is possible that some of the genetic traits predisposing horses to RAO are sex-linked, or that environmental exposures of females (e.g., broodmares) are different from the environmental exposures of males.

The review team had set out to investigate the scientific literature on the effects of gender aspects on allergies in cats, dogs or horses.

“In general, information about the influence of sex hormones in allergic disorder in companion animals is very limited,” they concluded.

In most cases, domestic cats, dogs and male horses were castrated, which neutralized any effects of sexual hormones.

“The impact of sexual hormones on canine, feline or equine allergic diseases is an interesting research field and can help in finding comparative aspects in relation to human allergies, due to the neutering performed in companion animals.”

However, more information would be needed on animals to investigate this area further.

“The foundation of central databases, where research centers or universities would document and share their patients’ records would be very helpful.

“Additionally, central state registers of all small animals (dogs and cats) and possibly horses, documenting species, date of birth, breed, gender, status/age of neutering, and diseases would be the next useful step in understanding hormonal influences.

“Data from commercial veterinary laboratories performing allergy testing may also – to a certain degree – be valuable.

“In addition, longitudinal studies that would follow the relationship between the neutering of allergic dogs or cats and the amount of medication needed to control their atopic dermatitis might, to some degree, address our question.”

Gender aspects in allergies of pets – A secondary publication and update
Ina Herrmann, Lukas Einhorn and Lucia Panakova
World Allergy Organization Journal 2017 10:42 https://doi.org/10.1186/s40413-017-0172-1

The review, published under a Creative Commons License, can he read here

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