Lawrence R. Ash

Development of Brugia pahangi in the Jird, Meriones unguiculatus, with Notes on Infections in Other Rodents

Infective larvae of Brugia pahangi dissected from Armigeres subalbatus that had fed 8 to 9 days previously on an infected dog were inoculated subcutaneously into the testicular area of 42 jirds, Meriones unguiculatus. All animals became infected. Early developmental stages were recovered from the pelt, carcass, lymph nodes, fat, testes, heart, and lungs. The third molt occurred from 6 to 9 days and the fourth molt from 18 to 24 days postinfection. Males started the last two molts from 1 to 2 days earlier than females. Twenty-five of 33 jirds developed patent infections with microfilaremias persisting for at least 13 weeks. Microfilarial densities varied considerably and appeared to be somewhat dependent on the size of the larval inoculum used. Jirds infected with 10 to 50 larvae usually developed low microfilaremias; high microfilarial densities were frequently see following inoculation of 70 to 100 larvae. The mean prepatent period for all infections was 67 days; the shortest time was 57 days, the longest 84 days. Adult worms were usually found either in the heart and lungs or in the testes, but the highest and most stable microfilaremias occurred in animals with a majority of worms in the testes. Other potential rodent hosts investigated included a second species of jird, M. libycus, a wood rat, Neotoma lepida, a kangaroo rat, Dipodomys merriami, and golden hamsters. Developing worms were found in all but the kangaroo rats, but microfilariae were produced only in M. libycus. Worms were found almost exclusively in the heart and lungs of these other rodents. Attempts to infect small rodents with lymphatic-dwelling filarial worms of man and other vertebrates have generally been unsuccessful. Probably the most concerted effort was that of Ramachandran and Pacheco (1965) who achieved limited success with Brugia pahangi in cotton rats. Other workers, Laing et al., 1961; Edeson et al., 1962; Zaini et al., 1962; Ahmed, 1967a, b; and Chong and Wong, 1967, tried to establish either B. pahangi or subperiodic B. mialayi in mice, rats, hamsters, and other rodents with little or no success. The need for a susceptible small animal host for studies on the biology, host-parasite relationships, and chemotherapy of human filariae has been stressed repeatedly (WHO Tech. Rep. No. 359, 1967). The ability of jirds to serve as suitable hosts for a variety of helminth infections suggested their possible usefulness as hosts for filariae of the genus Brugia. This study reports on the experimental transmission of B. pahangi to the jird, Meriones unguiculatus. Received for publication 13 February 1970. * This investigation was supported by the United State-Japan Cooperative Medical Science Program administered by the NIAID of the NIH, Department of Health, Education, and Welfare, U. S. Public Health Service Research Grant AI-07770. MATERIALS AND METHODS A dog infected with B. pahangi was obtained in 1968 from Parke, Davis and Company; this strain originated in Malaysia and was brought to the United States in 1958 where it was maintained in cats and dogs (Schacher, 1962). A Singapore strain of Armigeres subalbatus, maintained in the insectary of the Division of Infectious and Tropical Diseases at UCLA, was used as the vector mosquito (Barr, 1964). Mosquitoes were fed on an anesthetized dog that had a microfilarial density of 200 to 400 per 20 mm3 of blood at the time of exposure. Infected mosquitoes were then maintained at a temperature of 24 to 26 C and a relative humidity of 70 to 80% for 8 to 9 days prior to their dissection. Mosquitoes were stunned in test tubes immersed in an ice bucket and were then divided, using fine forceps, into head, thorax, and abdomen. These parts were immediately placed in tissue culture fluid (Medium NCTC 135, available from North American Biologicals, Inc., 16500 N.W. 7th Avenue, Miami, Florida), at a pH of 6.7 to 6.9, in a Baermann funnel. Larvae rapidly migrated out of fragmented mosquitoes and settled to the bottom of the funnel. They were then drawn off and counted. Larvae handled in this manner did not adhere to the glassware, and remained active for several hours, provided the fluid did not become alkaline. This was superior to dissecting mosquitoes individually in terms of time and labor involved and the numbers and vigor of larvae obtained. The rodent hosts used were: Meriones unguiculatus, the dark-clawed mongolian jird; a second jird species, M. libycus; two native California rodents, Neotoma lepida, a wood rat, and Dipodomys merriami, a kangaroo rat, and commercially obtained

Baylisascaris procyonis: An Emerging Helminthic Zoonosis

Baylisascaris procyonis, a roundworm infection of raccoons, is emerging as an important helminthic zoonosis, principally affecting young children. Raccoons have increasingly become peridomestic animals living in close proximity to human residences. When B. procyonis eggs are ingested by a host other than a raccoon, migration of larvae through tissue, termed larval migrans, ensues. This larval infection can invade the brain and eye, causing severe disease and death. The prevalence of B. procyonis infection in raccoons is often high, and infected animals can shed enormous numbers of eggs in their feces. These eggs can survive in the environment for extended periods of time, and the infectious dose of B. procyonis is relatively low. Therefore, the risk for human exposure and infection may be greater than is currently recognized.

Parasites in Human Tissues

Since there are myriad books in the field of parasitology and tropical medicine, the question one is likely to ask when first confronted with the title of this book is whether it is yet another parasitology text. Parasites in Human Tissues is neither a general parasitology text nor a tropical medicine text. For example, in the malaria selection the authors describe the malarial parasite within vessels and in tissues such as the liver. If one is in need of aid in the identification of the blood stages of the various malarial parasites, one should seek out standard parasitology texts or atlases. Similarly, this volume is not a reference for the morphology of intestinal protozoa or helminths. There is a companion Atlas of Parasitology that can be used for such purposes. Parasites in Human Tissues, however, is a superb reference text for the histological diagnosis of parasites. The book is divided into the familiar, albeit arbitrary, divisions that have become part of any parasitology text, namely, protozoa, nematodes, trematodes, and arthropods; in addition there is a valuable section on artifacts. Series of helpful colorful charts in the beginning of the book assist the reader in understanding both the usual and the unusual locations of parasites within host tissues. For each parasite, there is a short summary of the biology and life

Preferential susceptibility of male jirds (Meriones unguiculatus) to infection with Brugia pahangi.

In two trials, 17 litter-mate pairs of jirds (Meriones unguiculatus) were inoculated subcutaneously in the groin with infective-stage larvae of Brugia pahangi to determine if sex of the host was a factor in establishing infection. The mean prepatent period for 14 male jirds ranged from 67 to 76 days. Only 2 female jirds developed peripheral microfilaremia, one at 87 and the other at 94 days postinoculation. In 3 other females, microfilariae were found only in cardiac blood. More adult worms were recovered from male animals than from females; for males the percentage of inoculum recovered was 1 to 32%, in females it was 0 to 18%. In males, adult worms were found primarily in the testes and the heart and pulmonary arteries, whereas adult worms occurred almost exclusively in the heart and pulmonary arteries of female jirds. It appears that male animals, for unexplained reasons, are more susceptible to infection with lymphatic-dwelling filarial worms than are females. Earlier studies on the development of Brugia pahangi and subperiodic B. malayi in jirds indicated that male hosts appeared to be more readily infected than females (Ash and Riley, 1970a, b). This report summarizes observations made on two series of litter-mate pairs of jirds inoculated with B. pahangi to determine if one sex was more susceptible to infection than the other. MATERIALS AND METHODS The origin of the strain of B. pahangi used here was as reported earlier (Ash and Riley, 1970a). Armigeres subalbatus and Aedes aegypti (Liverpool strain) served as vector mosquitoes and were fed on an anesthetized cat that had a microfilarial density of 100 to 200 per 20 mm3 of blood. Maintenance of mosquitoes and the recovery of infective-stage larvae from them were as previously described (Ash and Riley, 1970a). Litter-mate pairs of Meriones unguiculatus, 4 to 6 weeks old, from a colony maintained in the UCLA Vivarium, were used. Male and female animals were inoculated alternately by pipetting a known number of larvae into a subcutaneous pocket close to the left testis in males and into the left groin in females. Animals were bled at weekly intervals beginning 56 days after inoculation; the prepatent period was computed as the mean day between the last bleeding in which no microfilariae were found and the day on which microfilariae were first found. The techniques of bleeding and Received for publication 12 January 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, U. S. Public Health Service Research Grant AI-07770. necropsy of infected animals were as previously described (Ash and Riley, 1970a).

Brugia pahangi: Depressed mitogen reactivity in filarial infections in the jird, Meriones unguiculatus

Abstract The phytohemagglutinin (PHA) and concanavalin A (Con A) reactivity of splenocytes from jirds, Meriones unguiculatus , with Brugia pahangi infections was found to be depressed in comparison to age-matched normals. The loss in mitogen reactivity (MR) could not be restored by increasing the concentration of mitogen in culture and the dose response curve of infected and normal animals was identical. No inhibitory factors were found in the sera of infected jirds that suppressed the MR of normal splenocytes and attempts to elute a depressor substance from the spleen cells of infected animals were unsuccessful. Further investigation revealed that the loss in PHA responsiveness was inversely correlated to the appearance of filarial-antigen sensitive cells in the spleen. This relationship suggested that the depressed MR was caused by filarial-antigen sensitive cells or cells cooperating with them in an immune response to the parasite. This hypothesis was supported by experiments which indicated that full MR could be restored to depressed cultures by removing adherent and phagocytic cells with nylon column, petri dish and iron/magnet technics. Further, it was found that the restored reactivity of column-purified cultures could be suppressed by mixing them with depressed unpurified isogeneic splenocytes. Thus it appears that experimental filariasis may induce suppressor cell activity that inhibits lymphocyte proliferation in vitro . The nature of these cells and the significance of depressed MR is discussed.

The ultrastructure of adult Brugia malayi (Brug, 1927) (Nematoda: Filarioidea).

The ultrastruct of the adult subperiodic Brugia malayi (Brug, 1927) within pulmonary arteries of male jirds (Meriones unguiculatus) was studied by transmission electron microscopy. The cuticle consists of 10 sublayers (2 of which are prominently banded) and a typical outer unit membrane. Evidence is presented showing that the subcuticular region of the lateral chords comprises a functional complex of basal infoldings, multivesicular bodies, and associated mitochondria, which is probably engaged in the exchange of solutes across a permeable cuticle. Microbodies with paired, prominent cores, intracisternal A-particle viruslike bodies, nonstaining glycogen patches, and other structures are also present in the lateral chords. The platymyarian somatic musculature shares some coelomyarian characteristics, e.g., apparent neuromuscular connections and prominent glycogen deposits surrounded by mitochondria and other organelles. The alimentary tract has features typical of many nematodes. The luminal segments of the male and female reproductive tracts and their germinal products, excluding microfilariae, are described. Affinities with related species are discussed.

Helminth parasites of dogs and cats in Hawaii.

The role of animal parasites, particularly those of the common household pets, in producing human disease has become increasingly apparent (Beaver, 1958). Such parasites as Toxocara spp., Ancylostoma spp., Trichuris vulpis, Dirofilaria immitis, Dipylidium caninum, and others have all been found in man. Thus, the knowledge of parasites of these animals in a community has both veterinary and public health interest. In this report, a list is given of helminths found in dogs and cats from the Island of Oahu, Hawaii. Included are observations on the distribution and life history of some of the parasites. Brief reports on parasites of dogs and cats in Hawaii have already been made by Hall (1936), Swanson (1939), Dikmans (1945) and Alicata (1947).

The lymphatic pathology of Brugia pahangi in the Mongolian jird.

We studied the sequence of histopathologic changes associated with Brugia pahangi (Nematoda: Filarioidea) infections in lymphatic vessels in the spermatic cord of the Mongolian jird (gerbil), Meriones unguiculatus. Intravascular granulomas caused mainly by disintegrating worms were seen in 67% of jirds necropsied on, or after, 35 days postinoculation, whereas none of 20 jirds examined before this day showed dying larvae. These granulomas usually evolved without vascular occlusion. Other granulomatous foci, often with a thrombuslike core, sometimes harbored microfilariae or microfilarialike materials. The perilymphatic cellular infiltrate consisted mostly of eosinophils, lymphocytes, and plasma cells. Large numbers of eosinophils were seen in the early weeks, but later declined, while lymphocytes increased to become the predominant cell in old infections. Irregular fibrosis of some valves and portions of the lymphatic walls were seen as early as the 2nd wk postinoculation. Lymphatic changes in the jird are similar to those described in other hosts infected with filariae, but remained moderate. Living worms appeared to be the stimulus for many observed changes. Most pathologic alterations were well established by 3 or 4 mo and showed little qualitative change during the remaining 4 mo of the study.

Cysticercosis-related Deaths, California

Cysticercosis is an increasingly important disease in the United States, but information on the occurrence of related deaths is limited. We examined data from California death certificates for the 12-year period 1989–2000. A total of 124 cysticercosis deaths were identified, representing a crude 12-year death rate of 3.9 per million population (95% confidence interval [CI] 3.2 to 4.6). Eighty-two (66%) of the case-patients were male; 42 (34%) were female. The median age at death was 34.5 years (range 7–81 years). Most patients (107, 86.3%) were foreign-born, and 90 (72.6%) had emigrated from Mexico. Seventeen (13.7%) deaths occurred in U.S.-born residents. Cysticercosis death rates were higher in Latino residents of California (13.0/106) than in other racial/ethnic groups (0.4/106), in males (5.2/106) than in females (2.7/106), and in persons >14 years of age (5.0/106). Cysticercosis is a preventable cause of premature death, particularly among young Latino persons in California and may be a more common cause of death in the United States than previously recognized.

Development of Gnathostoma procyonis Chandler, 1942, in the first and second intermediate hosts.

(Chandler, 1941, 1942). Since then this parasite has been found in raccoons in Georgia (Babero and Shepperson, 1958, 1959; Jordan and Hayes, 1959), Louisiana (Ash, 1960), and Florida (Orihel, 1960, personal communication) and its larval stage has been reported from water snakes in Louisiana (Miyazaki and Ash, 1959). The larval development has been described for three other gnathostomes: G. spinigerum (Owen, 1836), reported by Prommas and Daengsvang (1933, 1936); G. nipponicum (Yamaguti, 1941), reported by Arita (1953) and Mabuchi (1957); and G. doloresi (Tabangui, 1925), reported by Ishii (1956). These studies have shown that only cyclopoid copepods serve as first intermediate hosts and that various cold-blooded vertebrates are second intermediate hosts. It has also been demon-