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Dipetalonema gracile is a common parasite in squirrel monkeys (Saimiri sciureus), which can cause malnutrition and progressive wasting of the host, and lead to death in the case of massive infection. This study aimed to identify a suspected D. gracile worm from a dead squirrel monkey by means of molecular biology, and to amplify its complete mitochondrial genome by polymerase chain reaction (PCR) and sequence analysis. The results identified the worm as D. gracile, and the full length of its complete mitochondrial genome was 13,584 bp, which contained 22 tRNA genes, 12 protein-coding genes, two rRNA genes, one AT-rich region and one small non-coding region. The nucleotide composition included A (16.89%), G (20.19%), T (56.22%) and C (6.70%), among which A + T = 73.11%. The 12 protein-coding genes used TTG and ATT as start codons, and TAG and TAA as stop codons. Among the 22 tRNA genes, only trnS1AGN and trnS2UCN exhibited the TΨC-loop structure, while the other 20 tRNAs showed the TV-loop structure. The rrnL (986 bp) and rrnS (685 bp) genes were single-stranded and conserved in secondary structure. This study has enriched the mitochondrial gene database of Dipetalonema and laid a scientific basis for further study on classification, and genetic and evolutionary relationships of Dipetalonema nematodes.

Dipetalonema gracile is a common parasite in squirrel monkeys (Saimiri sciureus), which can cause malnutrition and progressive wasting of the host, and lead to death in the case of massive infection. This study aimed to identify a suspected D. gracile worm from a dead squirrel monkey by means of molecular biology, and to amplify its complete mitochondrial genome by polymerase chain reaction (PCR) and sequence analysis. The results identified the worm as D. gracile, and the full length of its complete mitochondrial genome was 13,584 bp, which contained 22 tRNA genes, 12 protein-coding genes, two rRNA genes, one AT-rich region and one small non-coding region. The nucleotide composition included A (16.89%), G (20.19%), T (56.22%) and C (6.70%), among which A + T = 73.11%. The 12 protein-coding genes used TTG and ATT as start codons, and TAG and TAA as stop codons. Among the 22 tRNA genes, only trnS1AGN and trnS2UCN exhibited the TΨC-loop structure, while the other 20 tRNAs showed the TV-loop structure. The rrnL (986 bp) and rrnS (685 bp) genes were single-stranded and conserved in secondary structure. This study has enriched the mitochondrial gene database of Dipetalonema and laid a scientific basis for further study on classification, and genetic and evolutionary relationships of Dipetalonema nematodes.

Dipetalonema caudispina(Molin, 1858) andD. gracile(Rudolphi, 1809) (Filarioidea: Onchocercidae) are two of six known species of filarial nematodes that parasitize Neotropical non-human primates. Adult filariae were collected from the thoracic and abdominal cavities of 38 of 44 specimens ofSapajus macrocephalus(Spix, 1823) and nine of ten specimens ofCebus albifrons(Humboldt, 1812) (Primates: Cebidae), distributed in the Yavarí-Mirín river basin and used locally for human consumption. Co-occurrence ofD. caudispinaandD. gracileis reported for the first time, with a prevalence of 18.5% (10 of 54 hosts examined). Our finding ofD. caudispinaandD. gracilein cebids from the Peruvian Amazon constitutes a new geographical record for both filariae, two new host records forD. caudispina,and the first report ofD. gracileinS. macrocephalus. In addition, we provide morphometric data forD. caudispina, complementing the original description, as well as scanning electron microscopy details on the structure of the area rugosa and number of caudal papillae in males.

This paper reports the development of the canid filarial worm, Dipetalonema dracunculoides, in the brown dog tick, Rhipicephalus sanguineus by determining whether development is similar within larval, nymphal and adult stages of infected ticks. This study demonstrates that only infected nymphal ticks can support the complete development of the filarial worm. Infected larval ticks are not suitable intermediate hosts, nor are infected adults. Development depends on some stage-specific property of the vector, and the maturation to the infective stage is stimulated during the course of the nymphal-adult moult.

Blood samples from 50 dogs with episodic weakness and 50 clinically normal dogs, all belonging to hunting breeds, were examined for microfilariae using the modified Knott's method. The prevalence of microfilaraemia in dogs belonging to the episodic weakness group was 10% for Dirofilaria immitis, 30% for Dirolfilaria repens and 8% for Acanthocheilonema reconditum. In the clinically normal group, the figures were 14% for Dirofilaria repens and 4% for Acanthocheilonema reconditum. The overall percentage of dogs with microfilaraemia in the episodic weakness group was 44 and that of the clinically normal group 16, with a statistically significant difference (PDirofilaria repens, Acanthocheilonema reconditum) was 34% and 16% for the episodic weakness group and the clinically normal dogs, respectively, with no significant difference.

Acanthocheilonema viteae,Litomosoides cariniiandSetaria cerviwere found to actively synthesize proteinsin vitro. Different centrifugation fractions and their TCA-precipitable fractions were assessed for the distribution of newly synthesized proteins. Penicillin and streptomycin inhibited the process inA. viteae. The synthesis inS. cerviwas susceptible to puromycin, chloramphenicol, cycloheximide, neomycin and polymyxin B. The process inL. cariniiwas strongly blocked by puromycin while chloramphenicol had no significant effect.

Experiments were carried out to obtain additional data concerning the role of IgM antibodies, specific for the cuticular surface of the microfilariae (mf) ofA. viteae, in clearing microfilaraemia from high-and low-responder mice infected by transplanted adult worms. Although BALB/c mice, which sustain a chronic microfilaraemia, produced IgM mf surface-specific antibodies, the binding to target mf was weak when compared to that of antibodies from the serum of the resistant C57BL/10 mice. Furthermore, antibodies from BALB/c mice were not as efficient as those from C57BL/10 mice in promoting the adherence of immune or control leukocytes to mfin vitro. Evidence is provided to show that mf shed surface bound antibody. Although the results do not establish conclusively the mechanism underlying the contrasting response phenotypes of C57BL/10 and BALB/c mice, they provide support for the involvement of antibody in controlling microfilaraemia and suggest that quantitative and qualitative differences in the amount and affinity of IgM antibody specific for the mf surface, together with the natural tendency of the mf to shed surface bound antibody at 37°C. may combine to allow the former strain to clear microfilaraemia efficiently whilst the latter sustains a chronic infection.

The evolution of the life cycles of the members of the family Dipetalonematiidae Wehr, 1935 (Filarioidea) is considered in the light of existing knowledge of spirurid nematodes. The hypothesis that the life cycles of the dipetalonematids originated from life cycles similar to those ofDraschia megastoma, Habronema muscaeandH. microstomais considered to be incorrect. Alternatively, it is pointed out that in the primitive subfamily Thelaziinae Baylis and Daubney, 1926 there are forms with typical spiruroid life cycles (Rhabdochona ovifilamenta), forms with life cycles approaching those of the dipetalonematids (Thelaziaspp.), and forms with life cycles intermediate between these two (Oxyspiruraspp.). It is suggested that intestinal species similar toRhabdochonagave rise to the more specialized spiruroids and forms that left the gut (Oxyspirura, Thelazia) gave rise to the dipetalonematids.The dipetalonematids are believed to have originated from nematodes resembling the species ofThelaziaand having life cycles like those ofT. rhodesii, T. skrjabiniandT. gulosa. Some of these worms established themselves in subcutaneous tissues. LikeParafilaria multipapillosa, they released their eggs through a break in the skin of the definitive host, thus causing a skin lesion that attracted various haematophagous arthropods which finally became involved as intermediate hosts in the life cycle. Certain species like the members ofParafilariaandStephanofilaria(?) came to rely upon intermediate hosts that were unable to break the skin of the definitive host (Musca) and cutaneous lesions became permanent features of their life cycles. Other species became dependent upon intermediate hosts that could puncture the skin (mosquitoes, simuliids etc.) and skin lesions became unnecessary to the life cycle. The larvae of these worms then began to spread into the tissues of the skin, as found inStephanofilaria, Onchocerca, and some species ofDipetalonema, and the infective larvae developed the ability to penetrate into the wound made by the intermediate host and perhaps, in some cases, the intact skin. Ultimately the larvae of some species habitually entered, or were deposited into, the blood stream and the adult worms were then free to colonize the vertebrate body as their larvae would then be available to the intermediate host no matter where the latter fed on the body of the definitive host; this group of worms gave rise to the many members of the family Dipetalonematidae.The family Filariidae Claus, 1883 is briefly reviewed in the light of the above hypothesis. It is pointed out that many species, e.g. Diplotriaeninae Skrjabin, 1916, live in the air sacs of reptiles and birds and probably have life cycles similar to that ofDiplotriaenoides translucidus, i.e. the eggs pass through the lungs, up the trachea and out in the faeces. It is thought that these forms may represent a separate line of evolution from that which gave rise to the Dipetalonematidae. Certain genera (Lissonema, Aprocta), occurring in the orbits of birds, probably have life cycles likeThelaziaorOxyspirura. Many other genera occurring in superficial muscles and subcutaneous tissues (Squamofilaria, Ularofilaria, Tetracheilonema, Pelecitus, Monopetalonema) may release their eggs through some sort of skin lesion. Studies on these forms are urgently needed as the details of their life cycles may shed fresh light on the origins of the more specialized filarioids.

1. The morphology of the adult worms and the microfilariae are described of a new species of filarial worm, Dipetalonema manson-bahri.2. Dehpsylla crassipes Jordon, 192G, a flea specific to Pedetes surdasler, was found in nature to contain infective larvae which are believed to be those of D. manson-bahri.3. In the laboratory full development of D. manson-bahri was observed in Ctenocephalides felis and Xenopsylla cheopis.

1. Dipetalonema dracunculoides (Cobbold, 1870), has been found in dogs (Canis familiaris), in the Turkana District of Kenya and in a hyaena (Crocuta crocuta), in the Southern Rift Valley.2. The dimensions of six male and six female worms agree with previous descriptions from hyaenas and dogs in Africa and from dogs in Portugal.3. Infective larvae were found in seven out of ten Hippobosca longipennis taken from a heavily infected dog.4. Morphologically the infective larvae are similar to those of other Dipetalonema spp., but they are much larger, averaging 2,400μ in length and 35μ in breadth with a tail length of 85μ.5. In Africa the distribution of the parasite coincides with the distribution of H. longipennis on dogs and hyaenas.6. This is the first time that a hippoboscid fly has been incriminated as the vector of a filarial worm. It is suggested that many other filarial species may be transmitted by Hippoboscidae.

The model ofOnchocerca lienalismicrofilariae (mff) injected into CBA and T.O. strains of mice has been used to examine immunity to skin-dwelling microfilariae following exposure to a range of species oF nelmmms Mice which had received a primary infection withO. cervicalismff were significantly resistant to challenge withO. lienalismfT(58% reduction relative to challenge controls). Immunization with the uterine contents (eggs and mff) ofO. lienalis, O. gutturosaorO. volvulusconferred equivalent levels of protection agains challenge withO. lienalismff (66 to 75%). Similar results were obtained with immunizations in mice that employed either fresh or freeze-killed eggs ofO. gutturosa. Significant reductions in the recoveries ofO. lienalismff were also demonstrated following the intraperitoneal implantation of adult male worms ofO. gutturosa(30 to 52%), the adults of either sex ofDipetalonema viteae(60%), or after infection witnTrichinella spiralis(27 to 81%). Infections with the trematode,Schistosoma mansoni, had a negligible effect on mff recoveries. It is concluded that partial resistance in mice toOnchocercamff may be stimulated by factors, yet to be determined, that are neither stage nor species-specific.

The protein composition of various developmental stages ofDipetalonema viteaewas analysed on polyacrylamide slab gels in the presence of sodium-dodecylsulphate. When the total proteins of adult male and female parasites, microfilariae, eggs, and third-stage larvae were compared, apparent qualitative similarities between mature and immature filariae were observed. However, several stage specific components were also identified.

Mierofilariae of Litomosoides carinii and Dipetalonema viteae absorbed about ten times as much diethylcarbamazine (DEC) as did their adults, but bound much less. The higher uptake of DEC by the microfilariae might be related to the fact that DEC is microfilariae Binding of DEC: with the parasites supports the view that the microfilarcidal action begins with the fixation of the drug to the microfilariae.

An adult female Dipetalonema setariosum (Mönnig 1926) recovered from the pleural cavity of Meriones libycus and bearing an adherent cell mass was examined by means of electron microscopy. The host reaction consisted exclusively of macrophages and was associated with disruption of the cuticular membrane and invasion of the cuticle itself. There was no evidence of prior activity by other cell types. Initiation of damage appeared to be associated with the release of lysosomal enzymes by the macrophages. Within the reaction a localized breaching of the cuticle had occurred and cells had penetrated the internal tissues of the worm. It is suggested that macrophages may play a role in the elimination of effete worms from an established population.

The microfilarial level in the peripheral blood of Mastomys natalensis infected with the filarial parasites, Litomosoides carinii, Brugia pahangi, B. malayi and Dipetalonema viteae was monitored at two-hour intervals for 24 hours. The microfilariae of B. pahangi and B. malayi exhibited nocturnal and diurnal subperiodicity, respectively; no such periodicty was seen in L. carinii and D. viteae infections.The level of B. pahangi and D. viteae microfilariae in peripheral blood was significantly increased when the host was anaesthetized with diethylether or pentothal sodium. Ether-induced anaesthesia had no effect on tne level of B. malayi microfilariae but pentothal was most effective. The peripheral blood count of L. carinii microfilariae tended to decrease in the anaesthetized animals but the reduction was not statistically significant.

The structure of the cuticle of third and fourth stage larvae and of adultBrugia pahangi(Nematoda: Filarioidea) was studied by light microscopy and by transmission and scanning electron microscopy. The cuticle of these worms was basically typical of the class Nematoda and consisted of cortical, matrix, and basal layers. Finely spaced annulation grooves were present and their function is discussed.Descriptions of the cuticular ultrastructure of filarial nematodes are meagre. Studies on the cuticle of adult worms are limited to those of Kagei (1960, 1963) onSetaria cerviandLitomosoides cariniiand of McLaren and Hockley (personal communication) who examinedL. carinii and Dipetalonema vitea

Transplanted infections of Dipetalonema viteae and Brugia pahangi have been evaluated as tools for experimental chemotherapy. Attempts were made to establish these filariae in similar pharmacokinetic sites within the same host, so that direct comparisons of in vivo drug susceptibilities could be made. Unfortunately, it was not possible to establish B. pahangi in the subcutaneous tissues, the preferred site of D. viteae. Therefore, intraperitoneal B. pahangi and subcutaneously implanted D. viteae in gerbils were used for the study. D. viteae infections were significantly enhanced by concomitant infections with B. pahangi, while B. pahangi infection rates were unaffected by the presence of D. viteae. Experiments with amoscanate, CGP6140 and Mel W demonstrated the importance of employing both B. pahangi and D. viteae for antifilarial discovery work and the fundamental effect of parasite location on drug efficacy. D. viteae rapidly migrate from the peritoneal cavity of gerbils following implantation; twenty one hours after infection 73% of transplanted worms were found in the subcutaneous tissues. It was shown that the migration response could be used as a stringent parameter for demonstrating antifilarial activity. D. viteae were exposed to antifilarial drugs for 24 hours in vitro, washed and implanted into the peritoneal cavity of gerbils. At autopsy, 5 days later, 10−8M ivermectin and milbemycin D had prevented migration; CGP6140, amoscanate, suramin, flubendazole and furapyrimidone were also detected at −6M using this parameter. In all cases the migration response was more sensitive to drugs than parasite kill. Ivermectin's ability to inhibit worm migration through the tissues is discussed, with respect to the role of itinerant males in the reproductive cycle of Onchocerca volvulus.

A consistent and reproducible method is described for isolating pure populations of microfilariae ofLitomosoides carinii, Brugia pahangi, B. malayiandDipetalonema viteae, free of cells, from blood, by density gradient centrifugation on Percoll in 0.25M sucrose. The recovery of the microfilariae was 85 to 97%.

Adult worms of a filarial parasite have been found during a survey of cattle at Wau Municipal Abbatoir, Bahr El Ghazal Province, Sudan. Two intact male worms were recovered but no females have been encountered as yet. Both worms were found within intradermal tissues at the umbilicus, and came from separate animals of the longhorned variety of indigenous Zebu cattle, Bos indicus. They were unencapsulated in the tissues from which they were isolated by dissection, fixed in 10% (v/v) formal saline and examined by phase microscopy. Dimensions were calculated from camera lucida drawings and are given as mean values for the two specimens.

A survey for parasites has been undertaken in 20 mountain gorillas (Gorilla gorilla beringei) from the Eastern Congo Kivu province.Six full-grown (two males and four females), three adolescents (one male and two females), and eleven young gorillas were examined, some of them during several consecutive months. Nine autopsies were performed.No protozoa were discovered in the blood. Plasmodium parasites which are common in gorillas and chimpanzees from West Africa were never found in the Eastern Congo primates, including ten other gorillas examined previously and some fifty chimpanzees. Severe diarrhoea with a balantidiasis picture developed in two young gorillas. Autopsy revealed however an intensive infection with Oesophagostomum stephanostomum and resulting fatty degeneration of the liver. Oligotrichida belonging to the genus Troglodytella were commonly found in the intestinal tract. Oesophagostomum stephanostomum eggs were consistently present in the stools of the gorillas and autoinfection caused the death of several young gorillas 4 to 6 weeks after their capture.