Date: May 2000
Q: What is piro?
A: It's the end result of infection with a protozoa usually carried by by ticks.
Classic teachings state that acute infections are usually only seen in those with some form of immune compromise. Flulike symptoms rapidly evolve to include shaking chills, high fevers, hemolysis and pancytopenia. Fatalities have been reported. Visualizing Babesial forms on peripheral smears can make the diagnosis in this situation. in those with intact immune systems, a mild flulike illness appears one to two weeks after exposure and clears without treatment over six to eight weeks. In either case, it is imperative to test for Borrelia and Ehrlichia.
However, when co-infection exists, this acute presentation is much less
common, and it is rare to see parasite forms on smear. Signs of co-infection
include severe headaches, dizziness and encephalopathy out of proportion to the other Borrelial symptoms. Testing is not at all definitive, yet should include CBC, Babesia smear (very low yield), serologies (IgG and IgM) and if necessary, PCR of peripheral blood. Newer direct assays are currently being researched, as this is an active area of investigation. Always consider co-infection in your current Lyme patients who are not responding fully.
Equine piroplasmosis (EP) is a disease of Equidae (horses, donkeys, mules,and zebras) caused by protozoan parasites which invade the red blood cells,causing their destruction. Two species or protozoa, Babesia equi and Babesia caballi, are present in 90% of the world inhabited by horses. Only Canada, United States, Australia, Japan, England and Ireland are not considered to be endemic areas
. The disease is blood borne, and is generally transmitted by ticks and
other insects, however improper disinfection of hypodermic needle or other instruments could cause mechanical transmission.
B. caballi causes a less severe disease as only about 1% of the red blood cells are infected. Infections may not be apparent, but can persist 1 to 4 years, although they are eventually eliminated. They may be associated with poor appetite, poor performance, and weight loss.
B. equi infects up to 20% of red blood cells, leading to more severe
clinical signs with fever, anemia, icterus (jaundice) increased respiratory and heart rates, and enlargement of the spleen. The parasites destroy the red blood cells, giving anemia, and the released hemaglobin may cause icterus and a dark urine. Colic, constipation followed by diarrhea, and swelling of the legs can occur. Foals can be infected in utero, and can be aborted or born anemic and weak. . Animals with B. equi infections become life-long carriers.
The greatest risk for introduction of this disease into Canada or other
non-endemic areas is through trading of animals or international equestrian sports, where infected and non-infected animals are in contact.. Many disease free countries have the climate suitable for a foreign tick vector, or have ticks which could act as vectors. Diagnosis is through serological
techniques, and the complement fixation test is generally accepted, although both false positive and false negative tests may occur.
Piroplasms are not bacteria, they are protozoans. Therefore, they will not be eradicated by any of the currently used Lyme treatment regimens. Therein lies the significance of coinfections- If a Lyme patient has been extensively treated yet is still ill, suspect a piroplasm.
Just as in Lyme Borreliosis, the longer one has been infected, the longer the course of therapy must be. Similarly, clinical assessment is the only guide to treatment endpoint.
Treatment choices are limited. Pentamidine is a treatment given as daily IM shots- very painful, they cause sterile abscesses and permanent fibrousscars on the buttocks. More importantly, response is poor, and the patientrisks development of glucose intolerance. Clearly, not a first choice.
Clindamycin, 600 mg qid plus Quinine, 650 mg qid has been the published
standard but the suggested two week course is nearly impossible to tolerate(hearing loss, rash, fever, headache) and treatment failures have been reported.
Gentamicin in combination with either penicillin or a first generation
cephalosporin is used in treating livestock infected with piroplasms. There are only anecdotal reports of efficacy in Humans and the dose and duration of therapy (14+days) has not been well worked out. The main side effect is hearing loss from the gentamicin, and the need for IM or IV doses.
Mepron (atavoquone), 750 mg bid, has demonstrated efficacy, but should be given concurrently with azithromycin, 250 to 600 mg daily, or resistance may develop. Efficacy is by far the best with this combination, but surprisingly, Herxheimer-like reactions are almost always seen at the fourth day, and at the fourth week of therapy. Does this represent a newly described phenomenon in treating Piroplasms, or does this combination have heretofore unrecognized efficacy in killing Bb? Although I do not have the answer, I suspect the latter simply based on the familiar (in Bb) four-week
cycle. In late, longstanding cases, one month of treatment is the minimum, and four or more months are often needed. Problems during therapy include diarrhea, mild nausea, the expense of Mepron ($600.00 per bottle- enough for one month of treatment), and rarely, a temporary yellowish discoloration of the vision. Regular blood counts and liver panels are recommended during any prolonged course of therapy.
Peter Edmunds, NZ