Subconjunctival zoonotic Onchocerca in an Albanian man.

A case of subconjunctival infection with a zoonotic species of Onchocerca is described, in a 16-year-old Albanian man who had immigrated to Greece. This is the first report of human infection with Onchocerca in this tissue location and only the eighth report of zoonotic Onchocerca in man.

Zoonotic filariasis.

Filariae of animals, especially those of mammals, often infect humans and typically produce cryptic infections. These "zoonotic" infections have been reported from virtually all parts of the world including temperate zones. Infections may be symptomatic or not, and the parasites are found in surgical tissue biopsy specimens or, more rarely, are removed intact from superficial sites such as the orbit or conjuctivae. Typically, these worms tend to occupy tissue sites similar to those occupied in the natural animal host, with the exception of the eyes. Many kinds of filariae have been isolated from humans, including species of Dirofilaria, Brugia, Onchocerca, Dipetalonema, Loaina and Meningonema. Worms have been found in subcutaneous tissues, the heart and lungs, lymphatics, the eye, and the central nervous system. Specific identification of these filariae is based on their morphological features in histologic sections. Unfortunately, some of these worms cannot be identified even at the generic level. There are other species of filariae, presumed to be zoonotic, which produce patent infections in humans but are poorly and incompletely known. These include Microfilaria semiclarum and Microfilaria bolivarensis. It is probable that almost any filaria parasitizing animals can, under proper circumstances, infect humans and undergo some degree of development. Undoubtedly, additional species of filariae will continue to be isolated from humans in the future.

Subcutaneous dirofilariasis: single inoculum, multiple worms.

The present report describes an unusual case of subcutaneous dirofilariasis attributed to Dirofilaria repens. The patient, a 42-year-old caucasian male, who acquired the infection in Africa, presented on two different occasions, 10 months apart, with a sudden onset of symptoms and a living worm moving about in the periorbital tissues. Both worms were mature nongravid females. Based on the maturation of the respective reproductive systems and the volume and distribution of eggs in the reproductive tracts, it was concluded that both worms were in the same infecting inoculum. The first worm was at least two years old and the second was therefore 10 months older than the first. These observations indicate that the worms developed and resided in the tissues without eliciting any host response for two and three years.

Brugia beaveri: microscopic morphology in host tissues and observations on its life history.

The filaria Brugia beaveri is a parasite of raccoons (Procyon lotor) in Louisiana. Its microfilariae, which circulate in the peripheral blood without any periodicity, develop to the infective stage in mosquitoes. The filaria can be transmitted in the laboratory to other raccoons, the domestic cat, and jirds (Meriones unguiculatus). The prepatent period is 70-107 days depending on the definitive host. Adult worms are found in lymphatics and associated subcutaneous tissues of raccoons and in the heart, lungs, and testes of jirds. In host tissues, the parasite is recognized by its small diameter and the morphology of the body wall. There is a thin cuticle, which is characteristically thickened in the lateral fields; in males, a lateral, internal cuticular ridge is sometimes present. The hypodermis forms large lateral chords and less conspicuous dorsal and ventral chords. Muscle cells are coelomyarian; in females there is an average of 4 cells per body quadrant and in males about 4-6. Internal organs are easily identified as to type, but do not provide any clues to species identification.

Mansonella ozzardi: the course of patency in experimentally-infected patas monkeys.

Twenty-five of 30 patas monkeys (Erythrocebus patas) inoculated with varying numbers (35 to 135) of third-stage larvae of Mansonella ozzardi developed patent infections in an average of 163 days. There was no correlation between the size of the inoculum and the length of the prepatent period. Ten of the monkeys were monitored thereafter by regular blood examination for extended periods of time in order to characterize the onset, course and duration of patency. Typically, with the onset of patency, microfilaremias increased steadily, peaking at about 20 weeks and then decreased slowly stabilizing at low levels for up to 48 weeks. Thereafter microfilariae disappeared from the blood and occasionally reappeared in scanty numbers. Laparotomies and followup studies indicated that the spleen was involved in the suppression of peripheral microfilaremia as had been observed earlier in patas monkeys infected with Loa loa. In ten monkeys splenectomized after the initial "wave" of microfilaremia, it was observed that (a) 30% of the animals remained amicrofilaremic, (b) another 30% reestablished patent infections but microfilaremias were lower than presplenectomy levels, and (c) in the remaining 40%, levels of microfilaremia equaled or exceeded pre-splenectomy levels. Patent infections persisted for up to 212 weeks. One monkey splenectomized prior to inoculation with 87 larvae developed a patent infection with microfilaremia which persisted for 156 weeks. Three monkeys with low and high levels of microfilaremia bled at four hour intervals over a 28 hour period showed no evidence of periodicity in the microfilaria.(ABSTRACT TRUNCATED AT 250 WORDS)

Strianema venezuelensis gen. et sp. n. (Filarioidea: Onchocercidae) from Venezuelan armadillos (Dasypus spp.).

A new filaria, Strianema venezuelensis gen. et sp. n., is described from armadillos in Venezuela. The adults inhabit the subcutaneous tissues and the microfilariae are found in the skin and occasionally the blood. The adults, which are of small size (males 9.6 to 13.8 mm in length by 57 to 63 microns in diameter, females 18.3 to 26.3 mm in length by 95 to 120 microns in diameter), have a distinctly striated cuticle. This filaria resembles most closely the genus Cercopithifilaria, from which it can be distinguished by the absence of a buccal capsule or pre-esophageal ring, and 11 to 13 pair of caudal papillae, three or four pair of which are separated as a group anterior to the cloaca. The species, S. venezuelensis, can be distinguished from the three other species of filariae described from armadillos by the undivided esophagus, number and distribution of caudal papillae in the male, size and shape of the spicules, and the distinctive microfilaria. The microfilaria, which averages 280 microns in length, has a unique, slender, almost filamentous tail.

Onchocerciasis in a California dog.

A 15-year-old dog that had lived all of its life on ranches and at the Wildlife Waystation on the western edge of the San Gabriel mountains near Los Angeles, California, developed an extensive granulomatous lesion involving the right eye and associated tissues requiring removal of both the eye and the lesion. Microscopic examinations of the tissues revealed the presence of living and dead gravid female worms and male worms belonging to the genus Onchocerca. Unsheathed microfilariae presumed to be Onchocerca species were found in the skin as well. Because Onchocerca species are not natural parasites of dogs, it is presumed that this infection was acquired accidentally from bovine, equine, or other animal host sharing the environment. This appears to be the first published record of patent onchocerciasis in a dog.

Development of Mansonella perstans in the surrogate vector Aedes aegypti.

The biology of the human filaria Mansonella perstans has been poorly studied due in part to the lack of experimental animal models in which its life-cycle could be reproduced. In nature Culicodes spp. (and probably simuliids) are the vectors involved in disease transmission. In the present work Aedes aegypti black-eyed strain was experimentally infected with M. perstans microfilariae by intrathoracic inoculation of 8 to 15 parasites contained in 0.4-0.6 microliters of RPMI 1640. Concentration of microfilariae was achieved by means of a ficoll separation technique. A. aegypti were maintained at 26 degrees C and 80% relative humidity with a sugar-water diet, except on day 4 post-infection on which they received an uninfected blood meal. Larval development was slow, taking no less than 4 days to reach the sausage stage, which measured 95-100 microns in length. Molt to the second stage took place on the 6th day; the differentiation into a long muscular and glandular esophagus, and short intestine measuring approximately one fourth of the total larval length were the most significant changes. At the end of this period 4 small but well demarcated tail papillae were observed. The first third-stage larvae appeared at the 8th day post-infection, measuring 650 to 680 microns in length. Beyond the 10th day larvae with an average length of 750 microns were found in the thorax, head, and mouthparts. Four conspicuous tail papillae characteristic of the genus Mansonella were seen in all third-stage larvae.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary dirofilariasis: restudy of worms reported gravid.

A worm in the lung of a man in Colombia, whose death was caused by lymphoid leukemia, originally reported as Wuchereria bancrofti with embryos in the uterus, was re-examined and identified as a Dirofilaria sp. and its gravid condition confirmed. A Dirofilaria sp. in the lung of a man in Japan, reported as gravid, was found to be nongravid with sloughed fragments of lining of the uterus mistaken for microfilariae. Noteworthy in the Colombia case is the association of lymphoid leukemia in the host and the gravid condition of the worm.

Dirofilaria striata infection in a North Carolina child.

A living, adult female Dirofilaria striata was removed from the orbit of a 6-year-old boy living in Buncombe County, NC. The specific identification of the filaria was based on its size and the morphological features of the cuticle including the weak, irregular, longitudinal ridges and small but conspicuous lateral alae.

Zoonotic Brugia infections in North and South America.

Nine new zoonotic Brugia infections, 8 acquired in the United States and 1 in Brazil, are described. In each, a single worm was found in histological sections of lymph nodes or lymphoid tissues. In those from North America, 5 of the 8 worms were females, all were infertile, and only 3 were alive at the time the tissues were excised; all of the patients were male. A dead female worm was collected from a Brazilian male patient. In addition, 3 cases of filarial infections in the U.S., previously identified as Dirofilaria-, Dipetalonema-, or Brugia-like, are reviewed and reclassified as Brugia species on the basis of microscopic morphological features. Morphological features of male and female zoonotic Brugia species as they appear in the host tissues are described. The possible reservoirs of human infections are discussed.

Development of Brugia malayi and Dirofilaria immitis in Aedes aegypti: effect of the host's nutrition.

The purpose of the study was to establish the importance of single and multiple blood meals taken by a vector in the development of larval filariae, dwelling in tissues other than the fat body. The black eye strain of Aedes aegypti was used as experimental vector for Brugia malayi and Dirofilaria immitis, filariae species which develop in the flight muscles and malphighian tubules respectively. Under similar conditions, both filariae species molted for the first time on the 6th day and a second time on the 10th day, approximately. Mosquitoes took an infective blood meal through a membrane feeder and were subsequently maintained on 10% sugar water alone (group A) or received supplementary blood meals i.e., an uninfected blood meal before the first molt and another after it (group B), an early blood meal (group C) or a late blood meal (group D). It was observed that larval development to the 2nd stage was similar in all groups of both filarial species. Early and repeated blood meals were the most desirable nutritional schemes for the rapid maturation of D. immitis while a late blood meal appeared to yield the best development of B. malayi larvae. Both species of filariae from mosquitoes maintained on sugar water alone showed an uneven and slow rate of development. It is concluded that nutrients other than carbohydrates are the important factors for the rapid growth of filarial larvae.(ABSTRACT TRUNCATED AT 250 WORDS)

Loa loa: output of microfilariae in single pair infections.

The intent of the present study was to assess the production and release of microfilariae by a single female filaria, in an in vivo system. Experimental infections of Loa loa were established in baboons by implantation of juvenile worms, typically, one female and two or three males. Infected animals were bled weekly and the number of microfilariae counted. Microfilarial counts were converted to number of microfilariae per milliliter and then the total number of microfilariae present calculated for the total volume of blood. Weekly increases in microfilarial counts were calculated for each animal. During the primary wave of microfilariae, the average weekly increase ranged from 16,000 to 194,000 (ave. 74,000). This figure gave an average daily output of 10,000 microfilariae per female. During the secondary wave of microfilariae following splenectomy, the average weekly increase ranged from 83,000 to 270,000 (ave. 157,000), giving an average daily output of 22,000 microfilariae per female. It is postulated that this level of production occurs only during the early phase of infection and is markedly reduced after the microfilaremia plateaus. The results indicate that the shedding of microfilariae by the female worm does not occur necessarily on a daily or weekly basis, and that female worms do not shed uniform numbers of microfilariae over a given period of time.

The effect of repeated blood meals on the larval development of Dirofilaria corynodes in the fat body of Aedes aegypti.

The objective of the study was to determine whether blood meals taken by a vector subsequent to the infective one have any influence on the course of development of a filarial parasite in its tissue. The filaria Dirofilaria corynodes (von Linstow, 1899) was selected for study and the black-eye strain of Aedes aegypti served as the experimental vector. The microfilaria of D. corynodes develops to the infective stage in the fat bodies of the vector. Following an infective blood meal, mosquitoes were maintained on 10% sugar water alone (group A) or received supplementary blood meals i.e., an uninfected blood meal prior to the first larval molt followed by another after it (group B), an early blood meal (group C) or a late blood meal (group D). It was observed that additional blood meals after the infective one enhance the rate of larval development regardless of the timing of the feedings. An early blood meal, even if it is the only one, has a long-term significant effect on development. Repeated blood meals do not have an additive effect but tend to result in greater uniformity in larval size. A late blood meal also has a positive effect on development although the larval filariae do not grow or mature as rapidly as in the groups already mentioned. Larvae from mosquitoes fed on sugar water alone tended to develop at a slower rate and with less uniformity. It is concluded that infected mosquitoes taking one or more additional blood meals will yield a larger number of infective larvae in a shorter period of time.

Loa loa: development and course of patency in experimentally-infected primates.

Loa loa infections were studied in baboons, rhesus and patas monkeys. Animals were infected either by s.c. injection of third-stage larvae (L 3) or by surgical implantation of juvenile worms of known age, sex and number. Microfilaremia was first detected in baboons at 140 days following inoculation of L 3 and at 142 days and 143 days in patas and rhesus monkeys, respectively; the mean prepatent period was 151 days in baboons, 149 days in patas monkeys and 169 days in rhesus monkeys. The primary wave of microfilariae (mf) was suppressed by the spleen in all three primate species. In baboons, the initial wave of mf lasted from 11 to 46 weeks (mean: 22 weeks), whereas in patas monkeys it persisted for 47 to 60 weeks, and in rhesus monkeys for 1 to 2 years. Gross and microscopical changes in the spleen were noted in all three primate species and consisted of numerous granulomata in the red pulp underlying the capsule. A resurgence of mf was observed following splenectomy in all three species of monkeys. Postsplenectomy levels of microfilaremia typically exceeded presplenectomy levels. One pair of worms was sufficient to produce patent infections in monkeys for extended periods of time. However, levels of microfilaremia were lower than in monkeys which received 75 and 200 to 300 L 3, although some overlap in microfilaremias between groups did occur. Overall, there was no proportional relationship between levels of microfilaremia and numbers of adult worms recovered from monkeys at necropsy. It was observed that, in the primate host, Loa is a long-lived parasite. Living worms were recovered from the tissues as long as 9 years after inoculation and there was no reason to doubt that patency would have persisted for some time into the future. Adult worms were frequently observed moving freely in the subcutaneous tissues of the primate hosts, although no instance of Calabar swellings or the presence of worms in or around the eye were ever recorded. The primate model of loiasis is an especially useful system because of the predictability of the behavior of the parasite. In most regards, the behavior of L. loa in the primate host is comparable to observations on the parasi e in man.(ABSTRACT TRUNCATED AT 400 WORDS)

Loa loa: antibody responses in experimentally infected baboons and rhesus monkeys.

Antibody responses to Loa loa in experimentally infected baboons and rhesus monkeys were measured using an adult L. loa antigen in a kinetic enzyme-linked immunosorbent assay. Animals were infected with infective stage larvae or by transplantation of juvenile worms. There were no differences between host species in antibody response and there was no relationship between adult worm numbers recovered at necropsy and antibody level. Antibody levels tended to be inversely correlated to the number of circulating microfilariae and decreased concommitant with the onset of patency. Following an initial wave, suppression of the microfilaremia was observed. Although the microfilaremia recrudesced following splenectomy, no changes in the antibody levels were noted pre or postsplenectomy. An antibody response was not demonstrable in baboons infected by transplantation of juvenile worms. Although a primary suppression of the microfilaremia by the spleen still occurred.