AN ELECTROPHORETIC STUDY ON SERUM PROTEINS IN ARABIAN RACE HORSES NATURALLY INFECTED WITH Babesia equi

Electrophoretic patterns of serum protein in 12 Arabian race horses acutely infected with Babesia equi revealed a significant decrease in albumin (P<0.01) and beta globulins (P<0.05) where, alpha globulins fractions significantly (P<0.01) increased. No significant (P>0.05) changes were recorded in gamma globulins fractions and total serum protein.

CLINICAL AND HAEMATOLOGICAL FEATURES OF STRESS INDUCED BABESIOSIS IN BABESIA EQUI INFECTED INDIGENOUS HORSES

Studies on actively stressed 3. equi infected premuned indigenous polo horses, manifested severe clinical syndromes characterised by partial anorexia, hyperthermia, lethargy, extreme weakness, marked dehydration, ecchymotic third eyelid, pale mucous membranes, sternal recumbency and coma. Some horses showed complete anorexia, obvious colicy symptoms, watery blood, and haemoglobinuria. The haematological changes in the affected horses included highly significantly (P<0.01) low packed cell volume, reduced haemoglobin concentration, depleted red blood cell counts and highly significantly (P<0.01) depleted neutrophils and lymphocytes.

Apicoplast-Targeting Antibacterials Inhibit the Growth of Babesia Parasites

ABSTRACTThe apicoplast housekeeping machinery, specifically apicoplast DNA replication, transcription, and translation, was targeted by ciprofloxacin, thiostrepton, and rifampin, respectively, in thein vitrocultures of fourBabesiaspecies. Furthermore, thein vivoeffect of thiostrepton on the growth cycle ofBabesia microtiin BALB/c mice was evaluated. The drugs caused significant inhibition of growth from an initial parasitemia of 1% forBabesia bovis, with 50% inhibitory concentrations (IC50s) of 8.3, 11.5, 12, and 126.6 μM for ciprofloxacin, thiostrepton, rifampin, and clindamycin, respectively. The IC50s for the inhibition ofBabesia bigeminagrowth were 15.8 μM for ciprofloxacin, 8.2 μM for thiostrepton, 8.3 μM for rifampin, and 206 μM for clindamycin. The IC50s forBabesia caballiwere 2.7 μM for ciprofloxacin, 2.7 μM for thiostrepton, 4.7 μM for rifampin, and 4.7 μM for clindamycin. The IC50s for the inhibition ofBabesia equigrowth were 2.5 μM for ciprofloxacin, 6.4 μM for thiostrepton, 4.1 μM for rifampin, and 27.2 μM for clindamycin. Furthermore, an inhibitory effect was revealed for cultures with an initial parasitemia of either 10 or 7% forBabesia bovisorBabesia bigemina, respectively. The three inhibitors caused immediate death ofBabesia bovisandBabesia equi. The inhibitory effects of ciprofloxacin, thiostrepton, and rifampin were confirmed by reverse transcription-PCR. Thiostrepton at a dose of 500 mg/kg of body weight resulted in 77.5% inhibition ofBabesia microtigrowth in BALB/c mice. These results implicate the apicoplast as a potential chemotherapeutic target for babesiosis.

Persistently Infected Horses Are Reservoirs for Intrastadial Tick-Borne Transmission of the Apicomplexan Parasite Babesia equi

ABSTRACT Tick-borne pathogens may be transmitted intrastadially and transstadially within a single vector generation as well as vertically between generations. Understanding the mode and relative efficiency of this transmission is required for infection control. In this study, we established that adult male Rhipicephalus microplus ticks efficiently acquire the protozoal pathogen Babesia equi during acute and persistent infections and transmit it intrastadially to naïve horses. Although the level of parasitemia during acquisition feeding affected the efficiency of the initial tick infection, infected ticks developed levels of ≥104 organisms/pair of salivary glands independent of the level of parasitemia during acquisition feeding and successfully transmitted them, indicating that replication within the tick compensated for any initial differences in infectious dose and exceeded the threshold for transmission. During the development of B. equi parasites in the salivary gland granular acini, the parasites expressed levels of paralogous surface proteins significantly different from those expressed by intraerythrocytic parasites from the mammalian host. In contrast to the successful intrastadial transmission, adult female R. microplus ticks that fed on horses with high parasitemia passed the parasite vertically into the eggs with low efficiency, and the subsequent generation (larvae, nymphs, and adults) failed to transmit B. equi parasites to naïve horses. The data demonstrated that intrastadial but not transovarial transmission is an efficient mode for B. equi transmission and that persistently infected horses are an important reservoir for transmission. Consequently, R. microplus male ticks and persistently infected horses should be targeted for disease control.

Babesial Vector Tick Defensin against Babesia sp. Parasites

ABSTRACT Antimicrobial peptides are major components of host innate immunity, a well-conserved, evolutionarily ancient defensive mechanism. Infectious disease-bearing vector ticks are thought to possess specific defense molecules against the transmitted pathogens that have been acquired during their evolution. We found in the tick Haemaphysalis longicornis a novel parasiticidal peptide named longicin that may have evolved from a common ancestral peptide resembling spider and scorpion toxins. H. longicornis is the primary vector for Babesia sp. parasites in Japan. Longicin also displayed bactericidal and fungicidal properties that resemble those of defensin homologues from invertebrates and vertebrates. Longicin showed a remarkable ability to inhibit the proliferation of merozoites, an erythrocyte blood stage of equine Babesia equi, by killing the parasites. Longicin was localized at the surface of the Babesia sp. parasites, as demonstrated by confocal microscopic analysis. In an in vivo experiment, longicin induced significant reduction of parasitemia in animals infected with the zoonotic and murine B. microti. Moreover, RNA interference data demonstrated that endogenous longicin is able to directly kill the canine B. gibsoni, thus indicating that it may play a role in regulating the vectorial capacity in the vector tick H. longicornis. Theoretically, longicin may serve as a model for the development of chemotherapeutic compounds against tick-borne disease organisms.

Serodiagnosis of Babesia equi in horses submitted to exercise stress

A complement fixation test (CFT), performed in microtitre plates, based upon the use of crude antigenic preparation of Babesia equi was adapted for the detection of antibodies in serum of infected horses. The indirect fluorescent antibody test (IFAT) and enzyme-linked immunosorbent assay (ELISA) were also used for the immunodiagnosis of B. equi. Serum samples from 15 apparently healthy horses, previously conditioned to a high-speed equine treadmill, were taken before and after exercise. All the samples analyzed were positive for B. equi infection. There were no significant differences (P<0.01) between these 3 tests, or the condition of rest or stress. The combined use of CFT and IFAT or ELISA should be recommended in order to enable veterinary services to more efficiently prevent introduction of infected horses into disease-free areas.