oxytetracycline--anhydrous and Parasitemia

The paper reviews the infectivity, cross-immunization experiments, and cattle vaccination of Zimbabwean cattle-derived Theileria parva (Boleni) sporozoite stabilates produced at the Central Veterinary Laboratory (CVL) in Harare between 1980 and 2003. The Boleni stock was first isolated in July 1978 during a theileriosis outbreak and was shown to be virulent in susceptible cattle. Thereafter, the reactions observed in susceptible cattle produced by different tick stabilates derived from the original have been mostly severe (76%) or moderate (24%). The parasite concentrations in the Boleni vaccine, the vaccines used in East Africa, and a Malawian stock were compared. The infective Theileria sporozoite concentration in 1 ml of stabilate in the Muguga and Serengeti (from East Africa) and Kasoba (from Malawi) vaccines were 8×, 9×, and 14× the concentration of the Boleni stabilate, respectively. The Boleni strain, like the other Zimbabwean T. parva isolates, produces a characteristic low piroplasm parasitaemia of usually less than 1% in susceptible cattle. This has largely contributed to the difference in infection rates (1963; average 40%) among tick batches used to prepare the various stabilates. Subsequently, the sporozoite concentrations in 1 ml of stabilate also varied considerably (6-91; average 53), making the reproducibility and standardization of the stabilates for immunization difficult. Immunization of cattle using Boleni stabilates with oxytetracycline therapy or with titrated low doses without treatment was found to be safe and efficacious. Cross-immunity experiments demonstrated that T. parva Boleni stabilates cross-protected against all the Zimbabwean cattle-derived T. parva stocks tested. The characteristics of the Boleni stock in affording a wide spectrum of cross-protection make it an excellent candidate for cattle immunization in Zimbabwe, hence protecting the country from the introduction of foreign vaccines and subsequently, foreign parasite populations.

Topics: Animals; Cattle; Cross Protection; Disease Outbreaks; Immunization; Malawi; Oxytetracycline; Parasitemia; Protozoan Vaccines; Reproducibility of Results; Rhipicephalus; Sporozoites; Theileria parva; Theileriasis; Zimbabwe

Anaplasmosis, caused by the tick-borne rickettsia, Anaplasma marginale, is an economically important disease of cattle in the United States and worldwide. Cattle that recover from acute infection become carriers in which low or microscopically undetectable A. marginale rickettsemia persists. Tetracycline antimicrobials are currently the only drug used in the US for treatment of acute anaplasmosis. There are currently no drugs specifically licensed for elimination of persistent infections. This study tested the efficacy of three oxytetracycline treatment regimens to clear A. marginale from cattle that were persistently infected. Forty Angus x Simmental steers, aged 6-12 months were experimentally infected with A. marginale. After the steers recovered from acute infection, seroconverted, and were confirmed infected using nested PCR followed by DNA hybridization, the carrier status of each animal was ascertained by sub-inoculation of blood into a separate, splenectomized Holstein calf. The steers were then blocked by bodyweight and randomly assigned as follows to four treatment groups: Treatment A, 300 mg/ml solution of oxytetracycline (Tetradure LA-300, Merial Canada Inc.) administered at 30 mg/kg, by intramuscular (i.m.) injection on day 0; Treatment B, the same 300 mg/ml solution of oxytetracycline administered at 30 mg/kg, i.m. on day 0 and again on day 5; Treatment C, a 200 mg/ml solution of oxytetracycline (Liquamycin LA-200, Pfizer Animal Health) administered at 22 mg/kg, intravenously (i.v.), q 24 h for 5 days (a treatment dose that corresponds with current Office International des Epizooties (OIE) recommendations for treatment prior to export). The fourth group consisted of untreated infected control cattle. All steers were still nested PCR and cELISA positive at 60 days after treatment. Infection was confirmed by subinoculation of blood into a splenectomized Holstein calf. These results demonstrated that the treatment regimens tested failed to clear A. marginale infections in carrier cattle.

Topics: Anaplasma marginale; Anaplasmosis; Animals; Antibodies, Protozoan; Antiprotozoal Agents; Carrier State; Cattle; Cattle Diseases; DNA, Protozoan; Enzyme-Linked Immunosorbent Assay; Erythrocytes; Hematocrit; Injections, Intramuscular; Injections, Intravenous; Male; Multivariate Analysis; Oxytetracycline; Parasitemia; Polymerase Chain Reaction

We have developed a mouse model for Babesia canis infection using severe combined immunodeficiency (SCID) mice whose circulating red blood cells had been substituted with canine red blood cells. Substitution of red blood cells in SCID mice was achieved by repetitive transfusions of canine red blood cells, together with administration of an antimouse red blood cell monoclonal antibody. Following inoculation of canine-red blood cell-SCID mice with B. canis, parasites proliferated in the canine red blood cells that had been transfused into the SCID mice, resulting in much higher parasitaemia than that observed in dogs. In an attempt to demonstrate the utility of this mouse model, three antiprotozoal drugs, diminazene diaceturate, clindamycin and oxytetracycline, were examined for their efficacy to inhibit the growth of B. canis in canine-red blood cell-SCID mice. The mouse model clearly showed that diminazene diaceturate and oxytetracycline were capable of eliminating B. canis from the canine-red blood cell-SCID mice, whereas clindamycin exhibited only a static effect as parasitaemia relapsed upon cessation of drug administration.

Topics: Administration, Cutaneous; Animals; Antibodies, Monoclonal; Antiprotozoal Agents; Babesia; Babesiosis; Cattle; Clindamycin; Diminazene; Dog Diseases; Dogs; Erythrocyte Transfusion; Erythrocytes; Female; Flow Cytometry; Male; Mice; Mice, SCID; Oxytetracycline; Parasitemia; Protozoan Infections; Protozoan Infections, Animal

Clinical and hematological changes of six Anaplasma marginale (isolated Zulia) inoculated calves (experimental group) and four healthy calves (control group) were studied during twenty and eighty days before and after infection, respectively. The behavior of the four calves used as control group was stable and no significant changes in the parameters analyzed was observed. The experimental group developed the three typical phases of illness. During the prepatent phase, which lasted a mean of 21.2 +/- 2.56 days, the animals were asymptomatic and no significant changes in the hematological values occurred, but a remarkable transitory decrease in number of lymphocytes from 6.5 x 10(6) to 3.3 x 10(6) cells/ml. The infection during the acute phase produced a highly severe effect in two animals, a severe effect in three animals and a mild effect in one. The effects observed were the following: 1) a fast decrease in haematocrite, ranging from 6 to 10%; 2) values of parasitaemia varied from 15 to 48%; 3) a greater body temperature than the control animals (40.5 vs. 38.5 degrees C); 4) a elevated heart frequency, from 60 to 110 beats/min; 5) an increase in the concentration of neotrophiles from 10 x 10(6) to 13 x 10(6) cells/ml; 6) The number of monocytes also augmented from 3 x 10(6) to 6 x 10(6) cells/ml; and 7) an important decrease of weight gain. The natural course of infection was interrupted with oxytetracycline when the haematocrite of the animal lowered to values less or equal to 10%. Then, the animals showed a rapid recovery with an undetectable parasitaemia and concomitant return to basal line of the rest of the parameters.

Topics: Anaplasmosis; Animals; Blood Cell Count; Body Temperature; Cattle; Heart Rate; Oxytetracycline; Parasitemia; Respiration; Weight Gain