1.During the past eighteen months 210 native wild monkeys and 43 native captive monkeys have been examined for parasites of the blood stream. The only difference the two groups show is a decrease in the intensity of the infections in most of the captive animals rather than any difference in parasite species.
2.Monkey malaria. The present state of our knowledge indicates that many infant monkeys of the prehensile tail species, especially the Ateles and Cebus species, die of this disease. We have observed four such deaths. Those that survive this period are moderately good carriers of the disease through the juvenile period of life. During adult life other diseases and particularly late stage pregnancy seem to provoke a recrudescence in some animals. In these species of monkeys the spleen weight shows a ratio of 2.5 to 4 grams to each pound of body weight while in those species in which malaria was not found the spleen rate was 1 gram to each pound of body weight. Malarial pigmentation of the spleen is common in the prehensile tailed species and not yet found by us in the other species. The malarial parasites found closely resemble human quartan and tertian malaria. Nothing that resembles P. falciparum has been found here.
3.Monkey trypanosomiasis. All species thus far examined by us show this parasite except Ateles dariensis. We have seen but one specimen of this monkey, a juvenile raised in captivity. Adults examined in the wild state will almost certainly show some individuals harboring this parasite. The infection appears to offer little injury to the animals and does not take in the ordinary laboratory animals into which it has been inoculated. Morphological studies will be reported at a later date.
4.Monkey filariasis. This is an important monkey disease, particularly in the Cebus and Ateles species. We have not yet examined a satisfactory number of the howling monkeys (Alouatta palliata inconsonans Goldman). There is a marked proliferative peritonitis present and in some cases a sero-purulent fluid is found. Vast numbers of adult-parasites are found in the omentum and also free in the cavity. Omental adhesions are common and occasionally pleural and pericardial adhesions also are present. Further studies are in progress and a report pending.
Filariasis in the titi species and the night monkey are of a different order. No adult parasites have been found by us in the cavities of the two did monkeys although their blood films are positive in almost every case.
5.Malaria is a disease of infant and juvenile life while trypanosomiasis and filariasis are chiefly noted among the adults.
6.Monkey spirochetosis. This has not been found spontaneously in any but the titi monkey commonly known as the squirrel monkey Leontocebus geoffroyi (Pucheron). It is fatal in most instances to infant and juvenile members of this species in captivity while an adult recovers spontaneously in a very few days. The rate of demonstrable infection in the wild is very low for adults. We have not been able to examine enough juveniles and infants in the wild to learn the incidence in them.
7.Our chief interest surrounds the possibilities of transfers of these infections to man or domestic animals and our efforts have been used in this direction rather than to complete the protozoological and pathological studies or to enter the equally interesting study of the parasites to be found in the alimentary tract. The old monkeys (in the wild) have much of interest in diseases of bones and joints and the genito-urinary system.
8.Ectoparasites. These are found but with great difficulty on the animal, although we have seen one severe louse infestation in the Ateles species. It is our belief that the ticks, lice and fleas common to these monkeys are more apt to be found at night while the animal is at rest in its favorite shelter. This of course confronts one with some major problems in observation yet it may be possible to study the dens of night monkeys, Aotus zonalis Goldman, since their habits are quite similar to those of squirrels.
Mosquito studies are in progress in relation to monkey malaria, and tick observations are under way in regard to possible transfers of the monkey spirochete.