Anaplasmosis/ Ehrlichia possible without having had swollen legs?
Just as the title reads, is it possible for a horse to have anaplasmosis or ehrlichia without having had swollen legs? It is suspected that my horse is infected, but he did not have leg swelling prior or while he has been sick.
The horse has been seen by a vet and my regular vet is coming out this afternoon to recheck and possibly do more diagnostics. I was just curious about this symptom that was absent in my horse.
To expand on what Chocomare said, equine monocytic ehrlichiosis is Potomac Horse Fever and more properly called neorickettsiosis, because ehrlichiosis doesn't have enough syllables. "Ehrlichiosis" usually refers to anaplasmosis or equine granulocytic anaplasmosis, which is spread by Ixodes ticks and therefore has a different spatial and temporal distribution and epidemiology than PHF, which is spread by insects with aquatic life stages, such as caddis flies and mayflies. The prime seasons for tickborne diseases are spring and fall, but this is not absolute. PHF is mostly seen in the hot summer months, when the insects mature and come out of the streams and rivers. PHF distribution is focal and spotty but nationwide; Anaplasma is seen wherever there are black-legged/deer ticks, Ixodes pacificus and Ixodes scapularis, so mainly in the eastern half of the country and along the Pacific coast and nearby foothills. These are the same tick species that spread Lyme disease, and a single tick may carry both diseases. Lyme disease may also cause a fever and vague signs at first, as well, or it may cause shifting lameness, uveitis, hypersensitivity, etc.
You do not need every clinical sign for a disease to be present! Both anaplasmosis and PHF can show up with vague signs such as fever of unknown origin, edema, depression, anorexia, etc., and signs vary from horse to horse, but PHF can cause large colon inflammation, causing anything from mild impaction colics or mild diarrhea to a horse that paint the walls with diarrhea and dies within a day or two due to fluid losses and/or laminitis. Since they live in blood cells, it is possible to do PCR on whole blood (best at the beginning of the illness, before treatment), and a blood smear may show the Anaplasma living in the neutrophils, although a negative blood smear is not as conclusive as PCR; PHF is much harder to find on a blood smear. Horses with diarrhea may be diagnosed with PHF by fecal PCR sometimes. Because Lyme/Borrelia does NOT live in the blood, blood PCR is less helpful and titers are usually used for diagnosis.
Fortunately, the basis for treatment for all of these is tetracycline antibiotics (oxytetracycline, doxycycline, minocycline), although regimens vary.
LOL, any time! The challenge sometimes is to make sure you don't use TOO much lingo for non-vets. I'm a total infectious disease nerd, and our week of vector-borne diseases was one of my favorite so far in vet school.