Evolution and diversity of the EMA families of the divergent equid parasites, Theileria equi and T. haneyi.

The equine parasite Theilera equi continues to curtail global equine commerce due primarily to its ability to persist indefinitely in the immunocompetent horse. Details regarding the parasite life cycle, pathogenesis and mechanism of persistence remain unclear. The recently discovered T. haneyi is also capable of persistence in the horse, creating a potential reservoir for additional infections. These two divergent parasites share a unique gene family that expresses surface merozoite antigens, or equi merozoite antigens (EMAs). The EMA family was maintained in number and size in both parasites despite a species divergence of over 30 million years ago. This family is unique amongst Theilerias in number, structure and biochemical properties. In silico analysis revealed no evidence of selection for diversity within this family, indicating a role in host adaptation and persistence rather than antigenic variation and immune escape. Biochemical analysis revealed the presence of a conserved domain, homologous to the hemolysin toxin found in cobra venom. This finding combined with data from protein interaction prediction models may indicate interaction with the structural components of the host erythrocyte and a role in merozoite entry or escape. Additional predicted protein interactions focus on disruption of the enzymatic functions of the host cell, potentially resulting in enhanced parasite survival.

Verification of post-chemotherapeutic clearance of Theileria equi through concordance of nested PCR and immunoblot.

Certain countries including the United States remain non-endemic for particular infectious diseases such as equine piroplasmosis through import restrictions and surveillance. Endemic regions often employ premunition as the primary method to control disease, however in non-endemic countries, chemosterilization combined with methods to confirm parasite elimination are required to maintain disease-free status. The ability of imidocarb diproprionate (ID) to clear persistent Theileria equi infection from infected horses has been shown through the inability of treated horses to transmit via blood transfer. However, the common lengthy persistence of anti-T. equi antibody causes regulatory tests such as cELISA or IFA to remain positive for extended periods. Persistence of positive testing creates challenges for regulatory veterinary medicine and international trade. Concordance between nested polymerase chain reaction (nPCR) targeting the ema1 gene and immunoblotting (IB) measuring declination in anti-EMA1 and anti-EMA2 antibody were used to verify clearance of T. equi from 179 ID-treated horses. These data support the use of IB to demonstrate declining anti-EMA1 and EMA2 titers in T. equi-infected horses subsequent to successful ID treatment. Such data provide concordant support to a negative nPCR and allow for a more timely determination of effective ID clearance of T. equi. The post ID treatment results indicate that while nPCR was consistently negative by 14 days and cELISA generally remained positive after 1 year, immunoblot was on average negative after 4 months and 100% in agreement with nPCR.

Review of equine piroplasmosis.

Equine piroplasmosis is caused by one of 2 erythrocytic parasites Babesia caballi or Theileria equi. Although the genus of the latter remains controversial, the most recent designation, Theileria, is utilized in this review. Shared pathogenesis includes tick-borne transmission and erythrolysis leading to anemia as the primary clinical outcome. Although both parasites are able to persist indefinitely in their equid hosts, thus far, only B. caballi transmits across tick generations. Pathogenesis further diverges after transmission to equids in that B. caballi immediately infects erythrocytes, whereas T.equi infects peripheral blood mononuclear cells. The recent re-emergence of T.equi in the United States has increased awareness of these tick-borne pathogens, especially in terms of diagnosis and control. This review focuses in part on factors leading to the re-emergence of infection and disease of these globally important pathogens.

A retrospective analysis of renal carcinoma in the horse.

BACKGROUND: Renal carcinoma is a rare tumor of horses. HYPOTHESIS: Presenting complaints and clinical signs of this disease are vague and early diagnosis increases survival time. ANIMALS: Data were collected from the medical records of 4 horses presented to Washington State University as well as the 23 previously published case reports of horses with renal carcinoma. METHODS: Retrospective study. RESULTS: Renal carcinoma affects horses of all ages with most cases observed in geldings and Thoroughbreds. The most common presenting complaints are nonspecific and usually do not occur until late in the course of the disease. Routine laboratory results generally are unremarkable with no evidence of renal dysfunction. Urine and peritoneal fluid analyses are consistently abnormal, but the changes usually are nonspecific. Rectal palpation often allows detection of an abnormal kidney or a mass in the area of the kidney. Renal ultrasound examination is the most rewarding imaging procedure, and when combined with renal biopsy, antemortem diagnosis can be achieved. Renal carcinoma is both locally invasive and metastatic, necessitating careful staging for metastasis using thoracic radiography and abdominal ultrasound examination. If the tumor is localized to 1 kidney, nephrectomy is the treatment of choice. No chemotherapy or radiation treatment for renal carcinoma has been reported in the horse. Median survival for this series of cases was 11 days (0 days-1 year). CONCLUSIONS AND CLINICAL IMPORTANCE: Prognosis is poor to grave.