Biomedical subjects
Publications and source records attributed to L L Logan.
A previously undescribed obligate intracellular bacterium was isolated from an aborted bovine fetus. The organism was resistant to penicillin, replicated within cytoplasmic vacuoles, exhibited structural characteristics compatible with the rickettsias, and shared antigenic determinants with Cowdria ruminantium.
Two groups of castrated male adult goats (three goats/group) were infected intravenously with the Ball 3 vaccine strain of Cowdria ruminantium and treated with long-acting oxytetracycline at the onset of clinical disease 10 days later. Five weeks post-vaccination one group was challenged with a Caribbean isolate (Gardel) and the other group with a West African isolate (Mali) of C. ruminantium. Non-vaccinated controls infected with either the Gardel or Mali isolate died. All of the vaccinated animals challenged with the Gardel strain reacted and survived. The three vaccinated animals challenged with the Mali isolate also reacted and two died of heartwater.
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Nine white-tailed deer (Odocoileus virginianus) were experimentally infected with Cowdria ruminantium, the causal agent of heartwater. All deer developed clinical signs; one was killed, one was treated, and seven died within 2 wk postinoculation. Diagnosis of heartwater was based on clinical signs, postmortem lesions and by microscopic observation of C. ruminantium in endothelial cells of brain capillaries of dead animals. Cowdria ruminantium was passaged by collecting blood from deer at the height of the febrile response and intravenous inoculation of susceptible deer and goats. Tetracycline was effective in the treatment of heartwater in a deer.
Blood collected in either sodium heparin or disodium edetate vacutainers from febrile goats infected with 4 isolates of Cowdria ruminantium and cryopreserved with 10% dimethyl sulphoxide at -70 degrees C and -196 degrees C was an effective stabilate to initiate heartwater infections in goats. A homogenized pool of whole Amblyomma variegatum ticks in Snyder's buffer, maintained at -196 degrees C, was used to infect a goat with C. ruminantium. Liver and spleen collected from Swiss mice infected with the Kwanyanga isolate of C. ruminantium were homogenized in Snyder's buffer, maintained at -196 degrees C and were used to initiate infections in mice. Fresh blood collected from febrile goats and maintained at 4 degrees C for as long as 72 h was infectious to mice. Neutrophils separated from blood of C. ruminantium infected goats and maintained in modified RPMI medium at 37 degrees C for 68 h were infectious for a goat. Similarly neutrophils from a 2nd infected goat maintained for 96 h at 37 degrees C were infectious for mice.
The sequential development of C. ruminantium (Kwanyanga and Kümm isolates) was followed in caprine leukocyte cultures by light microscopy, direct immunofluorescent microscopy (DFA), indirect immunoflourescent microscopy (IFA) and transmission electron microscopy (TEM). During the febrile response, one to several small cocci, large ring forms or rods were observed in neutrophils in blood smears and cytopreparations of neutrophil fractions using Diff Quik stain, Giemsa stain, DFA and TEM. One to several C. ruminantium colonies were seen in up to 35% of neutrophils maintained in vitro for 18 h to 5 days. The organisms were located in neutrophil phagosomes by TEM and were enveloped by two trilamellar unit membranes. Initially, C. ruminantium was tightly enclosed within phagosomes. At 20 h of incubation, organisms were frequently observed undergoing binary fission within enlarged phagosomal vacuoles. At later time periods, neutrophils harboured fully formed colonies (morula) containing numerous organisms. An occasional C. ruminantium-infected macrophage (Kümm isolate), and an occasional infected eosinophil (Kümm and Kwanyanga isolate) were found.
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Scheduled monitoring of tsetse and other biting flies at Tienfala Forest, Republic of Mali from December 1979 until June 1981 yielded more than 14,500 specimens. Comparisons of the monthly totals of tsetse and other biting flies with the monthly incidence of bovine trypanosomiasis in sentinel cattle suggested that biological transmission by a single riverine species of tsetse, Glossina palpalis gambiensis, accounted for most if not all disease transmission at the study site. The data obtained also suggested that human decisions had contributed to the magnitude if not the degree of the disease problem at the study site and that viable solutions to the disease problem exist.
Thirteen solutions were compared to determine the optimal diluent for preservation of the viability of the Kwanyanga isolate of Cowdria ruminantium. They included the 2 diluents commonly used with C ruminantium and diluents proved effective with other rickettsiae. The capability of each diluent to maintain the viability of C ruminantium over a 3-hour period at room temperature was assessed by comparing the survival distributions of groups of outbred albino mice after they were inoculated IV with infected liver homogenates. The results indicated that the Snyder I diluent was significantly better at maintaining the viability of C ruminantium than were the other diluents studied.
A study was initiated to evaluate two trypanocidal drugs, the prophylactic isometamidium chloride (Trypamidium) and the curative diminazene aceturate (Berenil) as to their potential for long-term maintenance of zebu cattle in a tsetse infested area of Mali. Trypamidium was administered quarterly and Berenil was administered only as animals were found to be positive for trypanosomes. During the 21-month study trypanosomiasis was the most frequently encountered disease in the cattle in the Berenil treatment group with an average of 5.5 reinfections. The predominant trypanosome species encountered was Trypanosoma vivax and the most important vector was Glossina palpalis gambiensis. The results indicate that, even though the direct costs for drugs under the two maintenance regimens were almost identical, the use of Trypamidium resulted in a significantly greater annual weight gain, prevented death loss due to trypanosomiasis and resulted in a herd with a greater market value.
A commercial goat dairy comprised of about 300 lactating does suddenly began to have a problem with polyarthritis in the kids and clinical mastitis in the does. The problem began 3 to 4 weeks following the introduction of 27 lactating does from a herd with a history of mastitis caused by Mycoplasma mycoides subsp mycoides (Mmm). Over 2 kidding seasons (about 12 months), approximately 170 kids and 70 does died or were euthanatized. Affected kids were 2 to 8 weeks old, had multiple warm swollen joints, body temperature of 40.8 to 41.5 C, marked weight loss, and pneumonia. All were lame and some experienced so much discomfort that they were unable to get up. The predominant necropsy finding was severe fibrinopurulent polyarthritis, but fibrinous pleuritis, fibrinous pericarditis, interstitial pneumonia, and bronchopneumonia also were found in some kids. Culturing of affected joints and of bulk tank milk yielded large numbers of Mmm. The outbreak was terminated by feeding heat-treated colostrum (56 C for 1 hr) and pasteurized milk to kids. Milk from the does was cultured repeatedly; by this procedure, the does shedding Mmm in the milk were identified and culled.
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