Effectiveness of enrofloxacin for the treatment of experimentally-induced bovine anaplasmosis / Eficácia da enrofloxacina no tratamento da anaplasmose bovina experimental

Four groups of six Holstein calves were inoculated with 3.6 × 10(7) erythrocytes parasitized with Anaplasma marginale. The criteria for treatment of calves were increasing A. marginale rickettsemia and 30% reduction of baseline packed cell volume (PCV) of each animal. Group 1 (G1) received 7.5 mg.kg-1 of enrofloxacin in a single dose; Group 2 (G2) 7.5 mg.kg-1 of enrofloxacin twice every three days; Group 3 (G3) 20 mg.kg-1 of long-acting oxytetracycline in a single dose; and Group 4 (G4) a single dose of PBS. Physical examinations, blood smears and PCV were performed daily. On day treatment, G1, G2 and G3 animals had a mean rickettsemia of 17, 23 and 12%, respectively. At 2 days after treatment (DAT) G1 and G2 animals showed a significant reduction of rickettsemia (p < 0.05) compared to G3. G3 animals had high rates of rickettsemia in the first 2 DAT and a slow decrease until stabilization on 9 DAT. The mean PCV in G1 and G2 increased and stabilized after 7 and 8 DAT, respectively. PCV stabilization was achieved in G3 at 13 DAT. Both enrofloxacin and oxytetracycline were effective for the treatment of anaplasmosis, but enrofloxacin was faster reduction of rickettsemia and PCV recuperation (p < 0.05) compared to oxytetracycline.

Quatro grupos de seis bezerros da raça Holandesa foram inoculados com 3,6 × 10(7) eritrócitos parasitados com Anaplasma marginale. Os critérios para o tratamento dos bezerros foram aumento da rickettsemia do A. marginale e redução de 30% do valor basal de volume globular (VG) de cada animal. O Grupo 1 (G1) recebeu 7,5 mg.kg-1 de enrofloxacina em dose única; o Grupo 2 (G2), 7,5 mg.kg-1 de enrofloxacina duas vezes a cada três dias; o Grupo 3 (G3), 20 mg.kg-1 de oxitetraciclina de longa ação em dose única; e o Grupo 4 (G4) uma única dose de PBS. Exames físicos, esfregaço sanguíneo e VG foram realizadas diariamente. No dia do tratamento, os animais G1, G2 e G3 apresentaram rickettsemia média de 17, 23 e 12%, respectivamente. Nos primeiros 2 dias após o tratamento (DAT) os animais do G1 e G2 mostraram uma redução significativa de rickettsemia (p < 0,05) em relação ao G3. Animais do G3 tiveram altas taxas de rickettsemia nos 2 DAT e uma diminuição lenta até à estabilização em 9 de DAT. O VG médio no G1 e G2 aumentou e estabilizou após 7 e 8 DAT, respectivamente. A estabilização do VG do G3 foi aos 13 DAT. A enrofloxacina e a oxitetraciclina foram efetivas no tratamento da anaplasmose, mas a enrofloxacina apresentou redução da rickettsemia e recuperação do VG (p < 0,05) mais rápida em comparação com oxitetraciclina.

Cambios clinicos y hematologicos en becerros infectados con Anaplasma marginale / Clinical and hematological change in calves infected with Anaplasma marginale

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 percent; 2) values of parasitaemia varied from 15 to 48 percent 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 percent. Then, the animals showed a rapid recovery with an undetectable parasitaemia and concomitant return to basal line of the rest of the parameters