Susceptibility of Mammalian Hosts to Larvae of Gnathostoma doloresi Tubangui 1925

Abstract

Gnathostoma doloresi is widely distributed in the South Pacific and Southeast Asia. The adult worm lives in tumors in the wall of the stomach and is commonly found in wild boars or rarely in pigs in the middle and southern areas of Kyushu, Japan. Miyazaki and Ishii (1952, Acta Med. 22: 467-473) and Ishii (1956, Fukuoka Acta Med. 47: 1474-1494) first discovered advanced third stage larvae encapsulated in two species of salamanders, the second intermediate hosts. The same larvae were found in snakes on Ishigaki Island, Okinawa, by Miyazaki and Kawashima (1962, Kyushu J. Med. Sci. 13: 165-169) and on Amami-Oshima Island, Kagoshima, Japan, by Tada et al. (1969, Jpn. J. Parasitol. 18: 280293). The infectivity and the migratory behavior of the larvae of G. doloresi in humans have not been established, thus a monkey and other mammals were experimentally infected with the larvae. In our experiments the larvae used for infection were isolated from snakes (Trimeresurus flavoviridis flavoviridis) captured on Amami-Oshima Island. The muscles of 20 snakes were minced, examined with a dissecting microscope and a total of 182 encapsulated larvae were recovered. These larvae were removed from the capsules in order to identify them as G. doloresi. One monkey (Macaca mulatta), one dog and one cat were each fed 20 infective larvae. The animals were necropsied 90 days postinfection and the gastric walls, intestines, livers, kidneys, lungs, hearts, and muscles were inspected for larvae. Two guinea pigs, three rats (SD strain), and two fowl were fed 10 larvae each, killed after 60 days and examined in the same manner. Five and eight larvae were recovered from the muscles of one monkey and one dog, respectively. They had increased in size, ranging from 3.2 x 0.36 to 5.7 x 0.51 mm in the monkey and from 3.6 x 0.43 to 4.8 x 0.46 mm in the dog, as compared with their size prior to inoculation which was 2.1 x 0.27 to 2.9 x 0.30 mm. Four larvae (2.8-3.6 x 0.370.40 mm in size) were from the muscles of one rat and six (2.8-3.5 x 0.38-0.52 mm in size) from two guinea pigs. None were detected in the tissues of one cat, two of three rats or the two fowl. In the rodents sacrificed at 60 days, most larvae were encapsulated in the muscles, whereas the larvae found in the monkey and the dog remained mostly free in the tissues at 90 days postinfection. The larvae recovered showed no morphological alteration but their body color had changed to bright, bloody red. This tint was much deeper in the free larvae, and such may have been caused by the accumulation of oxyhemoglobin in the body fluid following ingestion of red blood cells. These findings suggest that the larvae may move intermittently in the tissues and may be able to invade various other organs, as is the case with Gnathostoma spinigerum. Blood samples were collected at weekly intervals from the monkey, to prepare coverslip smear preparations for differential counts of leukocytes and to determine erythrocyte and leukocyte counts. In addition, the activities of glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), alkaline phosphatase and the albumin-globulin ratio were estimated in the serum until the animal was killed 90 days postinfection. Leukocyte counts were elevated up to 11.4 x 103/ mm3 during the 3rd wk and the increases were moderate during the 10th wk. Such a pattern of marked leukocytosis was caused primarily by an increase in the number of eosinophils (5 x 103/mm3). There were no significant changes in RBC counts. The blood chemistry examinations done to detect possible disorders of hepatic function if and when the larvae