Susceptibility of the Marmoset, Saguinus geoffroyi Pucheran, to Intraperitoneal and Oral Infections with Besnoitia (Protozoa: Toxoplasmea)

Abstract

Cystic and proliferative stages of two strains of Besnoitia darlingi (Brumpt, 1913) and a strain of B. jellisoni Frenkel, 1955 were highly pathogenic for marmosets, Saguinus geoffroyi Pucheran, when administered by either the intraperitoneal or oral route. The clinical picture of disease was similar for both routes of administration and resembled the acute form of the disease as seen in mice. There was a significant correlation between numbers of parasites in intraperitoneal inocula and the day of death. In general, death after oral administration occurred somewhat later than after intraperitoneal inoculation. But cystic B. darlingi killed more quickly than proliferative forms when both were given orally; however, individual variation in monkey hosts may have been as important as strain or stage of the parasite, with regard to time of death. Using relatively large numbers of organisms, all of 22 intraperitoneal infections and 21 of 26 oral infections proved fatal. Parasitemia was detectable at the time of death following both routes of inoculation. When the numbers of organisms were too small to establish a fatal infection they also failed to immunize. Protective immunity, detectable by subsequent intraperitoneal challenge, was established in two monkeys receiving large numbers of parasites by mouth. A monkey which became demonstrably immune to B. jellisoni (PN-3) was shown by heterologous challenge to be still susceptible to B. darlingi (D-3). Mouse-adapted Besnoitia darlingi (= B. panamensis) of lizard origin was reported to be experimentally pathogenic for Geoffroy's marmoset (Schneider, 1965). The disease in this animal was described as an acute, rapidly fatal infection accompanied by considerable ascitic fluid in which numerous proliferative forms of the parasite were found. The disease in the marmoset, in fact, very much resembled the disease in the mouse. The present paper presents the results of additional studies of marmoset besnoitiosis in which experimental infections were induced with either cystic or proliferative stages of three strains of Besnoitia by the intraperitoneal or oral route. MATERIALS AND METHODS Geoffroy's marmoset (Saguinus geoffroyi Pucheran) abounds in low forest and secondary growth throughout most of Panama. The monkeys could be obtained from street vendors during certain times of the year. If they survived in captivity the first few days, they did well on a diet of fruits supplemented with meat (grasshoppers or baby mice). They would sometimes accept adult mice, eating out the brains, muscles and viscera and throwing away the skin. Almost 100% had microfilariae in the blood and many were infected with a trypanosome. Received for publication 28 November 1967. * Present address: Parke, Davis & Company, 2800 Plymouth Road, Ann Arbor, Michigan 48106. A total of 53 marmosets were used in the present series of experiments. Administration was by the intraperitoneal or oral route. Intraperitoneal inoculations were made in the area of the right groin with a 21-gauge needle. Orally, parasites were delivered directly into the mouth of the hand-held animal from a small syringe without needle; if given slowly, permitting time to swallow, all monkeys readily accepted the dose once it had been tasted. To avoid trauma, stomach intubation was not used, and anesthetics were avoided as risky and