b'If your horse survives one of these 5 infections, he might still suffer lasting effectsChallengeSTACEY OKE, DVM, MSCvery day a passel of pathogens pokes and prods E at your horses immune system, trying to find a breach in the barrier. Even when horses look like theyre simply grazing peacefully in their pad-docks, their bodies are on full defense. On a daily basis, for instance, they might encounter: Soil-borne bacteria such as Rhodococcus equi in foals; Bacteria such as Leptospira (which causes leptospirosis), which live in pasture puddles, ponds, and streams;Mosquito-borne viruses such as West Nile virus and Eastern equine encephalitis;Other insect-borne bacteria, such as those that cause Lyme, piroplas-mosis, and anaplasmosis from ticks; Bacteria or viruses from herdmates or horses coming and going from equine facilities, including herpesviruses, equine influenza virus, coronavirus, Salmonella, and Streptococcus equi subspecies equi (strangles); and Parasites such as tapeworms and the causative agents of equine pro-tozoal myeloencephalitis (EPM).And as if the pathogens werent enough of a threat, theres also the toxins some can produceand might be found in foragethat can cause diseases such as botulism.Your horse often cant avoid these merciless microbes, which makes an optimally functioning immune system imperative. Luckily, most horses have fully functional immune systems; they just need a boost from time to time, in the form of vaccination, or help from antibiotics or from supportive care such as intravenous fluids, anti-inflammatory drugs, etc. After simple, straightforward infections such as rainrot or run-of-the-mill upper respiratory tract issues, most horses fully recover. In other cases patients potentially suffer long-term effects that nega-tively impact their performance and quality of life. In this article well learn which diseases most commonly cause post-infection illnesses, why some linger far past their welcome, and how they can impact long-term health, use, and quality of life.West Nile Virus (WNV)ISTOCK.COMThis virus crosses the blood-brain barrier and enters the central ner-vous system (CNS), where the brain and spinal cord lie. The resulting TheHorse.com | The HorseSeptember 201917'