Distribution of Developing and Mature Brugia malayi in Rhesus Monkeys and in the Jird, Meriones unguiculatus, after a Single Infection

Abstract

Ten rhesus monkeys (Macaca mulatta) and 20 jirds (Meriones unguiculatus) were each given a single inoculation of subperiodic Brugia malayi infective larvae in the rear foot by a puncture wound technique. The monkeys were killed after a period varying from 5 days to 25 weeks and the jirds from 2 to 32 weeks following inoculation. The individual recovery of worms from monkeys ranged from 0% to 40% with an average of 12%. Out of an overall total of 121 worms recovered from the 10 monkeys, 78 were found in the lymph nodes of the inguinal area, and 21 in the lymph vessels of the infected leg distal to the popliteal node. In jirds the individual recovery varied from 3% to 40% of the administered inoculum with an overall average of 207%; up to 6 weeks following infection, the majority were found in the lymph vessels distal to the popliteal node; from 7 to 32 weeks following infection, the majority were located in the heart and lungs with some worms recovered from the testes. This study confirms the production of patent infections of Brugia malayi in rhesus monkeys and in jirds. However, the levels of larval and adult recovery in both of these species is relatively low when compared with previously reported results using cats. This low rate of recovery, together with the more general distribution pattern in monkeys and the apparently pronounced migration in jirds, may be of importance in the selection of an experimental host for the study of Malayan filariasis. Of the several different vertebrates in which patent infection with Brugia malayi has been demonstrated, the domestic cat has most frequently been used for experimental studies. Recently we have described techniques for infection and recovery of this parasite that should facilitate future experimental studies using the cat as a model. However, at times it would be advantageous to have other models to use instead of, or in conjunction with, cats. It is commonly accepted that results from experiments using primates can more readily be extrapolated to man. Thus it was felt that if the techniques found to be useful in cats were found to be equally successful in a primate, certain studies such as preclinical drug studies or pathological studies could be carried out more effectively. Orihel and Pacheco (1966) demonstrated that at least the Philippine strain of B. malayi persisted in the rhesus monkey and therefore it might serve as a useful experimental host. On the other hand, a small animal Received for publication 20 May 1971. * This investigation was supported by the United States-Japan Cooperative Medical Science Program administered by the NIAID of the NIH, Department of Health, Education and Welfare. Grant No. AI 08260. t Permanent address: Box 32, Khartoum North, Sudan. model which would provide an inexpensive, easily handled host which could be used in drug screening programs would also be valuable. The jird, Meriones unguiculatus, has been shown to be a suitable host for Brugia malayi by Ash and Riley (1970). The present paper describes the results of distribution studies in rhesus monkeys and in jirds using methods previously found to facilitate observation and recovery of developing and mature Brugia malayi in cats. MATERIALS AND METHODS