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Virulent and Avirulent Strains of Babesia bovis : The Relationship Between Parasite Protease Content and Pathophysiological Effect of the Strain
Author(s) -
WRIGHT I. G.,
GOODGER B. V.,
MAHONEY D. F.
Publication year - 1981
Publication title -
the journal of protozoology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 0022-3921
DOI - 10.1111/j.1550-7408.1981.tb02815.x
Subject(s) - virulence , biology , parasite hosting , babesia bovis , microbiology and biotechnology , virology , strain (injury) , protease , babesiosis , enzyme , gene , genetics , biochemistry , anatomy , world wide web , computer science
A virulent strain of Babesia bovis (“L” strain) was rendered avirulent by irradiation with 35 krads with a γ source. Another virulent strain of B . bovis (“C” strain) was made avirulent by rapid blood passage through 12 splenectomised calves. Both the parent virulent and their respective avirulent strains were injected into susceptible cattle. A nonfatal disease was observed in those intact cattle that had avirulent parasites; however, a fatal disease was produced in those animals that had received virulent parasites and in splenectomised calves that had received avirulent parasites. Blood kinin levels rose and plasma kininogen levels fell significantly in those animals infected with both virulent strains. Nonsignificant changes occurred with these parameters in animals infected with avirulent parasites. Preparations of disrupted parasites were obtained from the four parasite populations. Both virulent strains contained high levels of protease. The avirulent forms contained insignificant amounts. As parasite doubling times and maximum parasitaemias were the same for all four parasite populations, we conclude that these enzymes are not obligatory for parasite multiplication in the vertebrate host. Their role in producing pathological changes in the host is discussed.