Pathological findings associated with Dipetalonema spp. (Spirurida, Onchocercidae) infection in two species of Neotropical monkeys from Brazil

Among vector-borne helminths, filarioids of the genus Dipetalonema (Spirurida: Onchocercidae) localize in several tissues and body cavities of several animal species, causing mild to moderate lesions. The pathological findings associated with Dipetalonema spp. infection in Neotropical monkeys from southern Brazil are herein described, along with a fatal case due to filarial polyserositis and entrapment of an intestinal segment. At necropsy, nematodes were observed in abdominal and thoracic cavities, or in the pericardium of 37 (31.3%) out of the 118 individuals examined (i.e., 35 Alouatta guariba clamitans and two Sapajus nigritus). In addition, at histology, 27.0% of positive animals presented microfilarie (inside blood vessels of lung, spleen, liver, and brain) and 8.1% presented adult nematodes in the heart, lung, and liver. In two cases, cross-sections of filarioids were associated with areas of epicardial thickening with intense fibrosis and pyogranulomatous inflammation in the brain, heart, liver, lungs, or spleen. The DNA fragment was amplify using the cox1 gene, sequenced and analyzed to identify the nematode species collected; presence of Wolbachia was assessed in the filarioids using the 16S rRNA gene. At BLAST analysis of the cox1 gene, 10 sequences showed 91.7% nucleotide identity with Dipetalonema gracile, and two with D. gracile (98.5%) and Dipetalonema graciliformis (98.3%). Phylogenetic analyses clustered sequences of the cox1 obtained in this study in two clades corresponding with the host species. Wolbachia sp. endosymbiont was detected in four samples. Data herein reported provide a description of pathological lesions associated with the infection by Dipetalonema spp., suggesting that they may cause disease in Neotropical monkeys. In addition, a better understanding of diversity and biology of Dipetalonema spp. in South America is needed to assess the impact they may cause in native non-human primates from Brazil.

Dipetalonema graciliformis (Freitas, 1964) from the red-handed tamarins (Saguinus midas, Linnaeus, 1758) in French Guiana

Six Dipetalonema species have been reported from Neotropical monkeys, Dipetalonema gracile, Dipetalonema graciliformis and Dipetalonema caudispina being the dominant species found in French Guiana primates. Adult filarioids isolated from the abdominal cavity of tamarins (Saguinus midas) in French Guiana were morphologically and molecularly identified as D. graciliformis. Phylogenetic analysis based on DNA and amino acid sequences of the cox1 gene as well as the concatenated sequences of the cox1 and the 18S genes indicated that D. graciliformis belongs to the clade 4 (ONC4) of Onchocercidae. Blast analysis of the 18S rDNA revealed that D. graciliformis in the studied tamarins is conspecific with the filarioid circulating in howler monkeys (Alouatta macconnelli) in French Guiana, previously referred to as unidentified Onchocercidae species.

Microscopic and molecular detection of Deraiophoronema evansi (Lewis, 1882) in domestic Bactrian camels (Camelus bactrianus) of Mongolia

Cameline filarosis is an important parasitic disease having an economic impact on the camel industry around the world. However, there has been no study on filarosis in Bactrian camels of Mongolia. Therefore, the aim of the present study was to detect and identify microfilariae of Deraiophoronema evansi (D. evansi) in Bactrian camels from three provinces, located in southern and southwestern Mongolia. Blood samples were obtained from 400 healthy two-humped camels of different ages and both sexes. All blood samples were analysed using a variety of diagnostic techniques. Microfilariae were detected in 30 Bactrian camels (7.5%) by the Knott technique, while 13 Bactrian camels (3.3%) tested positive in a direct smear test. D. evansi was detected in 18 Bactrian camels (4.5%) by PCR assay. Prevalence was shown to be high among Bactrian camels in the age group up to 5 years, while the lowest positive results were obtained for Bactrian camels in the 5-10-year age group and the over 10-year age group. To confirm the morphological identification, D. evansi-COI gene sequences were subjected to phylogenetic analyses. The D. evansi-COI gene sequences from Mongolian two-humped camels were identical to sequences from Iranian one-humped camels and were clustered together with these sequences in the phylogeny. This is the first report of molecular detection and identification of microfilariae of D. evansi in Bactrian camels of Mongolia.

A new species of Dipetalonema (Filarioidea: Onchocercidae) from Ateles chamek from the Beni of Bolivia

We describe a new species of Dipetalonema occurring in the body cavity of Ateles chamek (Humboldt, 1812) from north-central Bolivia. Morphologic characters serving to separate Dipetalonema yatesi n. sp. from known forms include a vagina vera with a simple tube and thin walls and a left spicule, which possesses a handle shorter than the lamina (ratio 2.7); the latter displays an anterior membranous alae similar in length to the terminal flagellum, a distal extremity of the left spicule within a simple hook and a membrane, phasmids at the basis of the lappets, and heterogeneous muscles occupying the whole cavity. Dipetalonema yatesi n. sp. can be separated from Dipetalonema robini, Dipetalonema gracile, and Dipetalonema graciliformis, between other characters, in having a simple vagina vera instead of a sinuous one, and from Dipetalonema caudispina and Dipetalonema freitasi in having the lamina of the left spicule divided in a membranous alae and a terminal flagellum.

CONCOMITANT IMMUNITY IN A RODENT MODEL OF FILARIASIS: THE INFECTION OF MERIONES UNGUICULATUS WITH ACANTHOCHEILONEMA VITEAE

In an attempt to study the occurrence of concomitant immunity in filarial infections, jirds (Meriones unguiculatus) were experimentally infected with Acanthocheilonema viteae, and patent animals were superinfected with a defined dose of A. viteae stage 3 larvae (L3). Infected animals harbored significantly less worms deriving from the superinfection than the control group (P < 0.05, 56.2%, and 63.4% protection), as shown by analysis of female worms 6 wk after superinfection on the basis of their developmental status and their length. This protection was not due to contact with L3 antigens because a significant reduction of worm burdens deriving of a superinfection was also observed after subcutaneous implantation of a single female worm (P < 0.05, 40.2% and 64.9% protection). The induced protective responses target L3 and restrict their migration because an established infection resulted in a reduction of L3 recovery (95.6% and 94.3%, P < 0.001) from tissues of jirds at day 5 after superinfection. Other data show that L3 from a superinfection are trapped within eosinophil-rich granulomas, which is likely to create unfavorable conditions for the worms and to lead to later death. Taken together, established A. viteae-infections partially protect hosts against homologous superinfection by an immune-mediated mechanism and, thus, regulate the population density of the parasites within the host by concomitant immunity.

Lethal LPS-independent side effects after microfilaricidal treatment in Acanthocheilonema viteae-infected rodents

Mastomys coucha and jirds infected with Acanthocheilonema viteae, a filarial species free of endosymbiontic bacteria of the genus Wolbachia, suffer lethal side effects after effective microfilaricidal therapy with diethylcarbamazine and levamisole, whereas, M. coucha infected with the Wolbachia-infested species Brugia malayi or Litomosoides carinii tolerate corresponding treatment. Mortality in A. viteae infected, treated animals varied with microfilariae density in the blood. It was up to 100% in highly microfilaraemic M. coucha and jirds, but low or absent in animals with low microfilariae counts. Deaths occurred in most cases 5-24 h after treatment. Characteristic symptoms in animals, which died subsequently were a rapid drop in body temperature by 4-7 degrees C, an increase in hematokrit values by up to 10% and a moderate blood acidosis. Lethal effects in A. viteae infections did not depend on a particular status of hypersensitivity of the animals since desensitization procedures, which protected infected M. coucha against an otherwise lethal intravenous challenge with A. viteae homogenate did not protect against adverse reactions to a subsequent microfilaricidal treatment. The animals were protected from treatment induced death by injection of N-LMMA. Thus the final morbific agent seems NO. The data show that adverse effects after effective microfilaricidal therapy may be caused by microfilariae derived components different from Wolbachia-released LPS.

Specific polymerase chain reaction for differential diagnosis of Dirofilaria immitis and Dipetalonema reconditum using primers derived from internal transcribed spacer region 2 (ITS2)

Both Dirofilaria immiti and Dipetalonema reconditum may be found in blood of infected dogs but it is not easy to distinguish D. immitis from D. reconditum in morphology. We cloned and sequenced the contiguous internal transcribed spacer (ITS) region, ITS1-5.8S-ITS2, of these two different parasites and published on GenBank as AF217800 for D. immiti and AF217801 for D. reconditum in this study. We designed two pairs of specific primers derived from ITS2 being used for polymerase chain reaction (PCR). The amplicons of ITS2 from D. immiti and D. reconditum are 302 and 348bp, respectively. Moreover, the limitation for amplifying ITS2 gene using this PCR demonstrated that 1 x 10(-2) microfilaria of each species of parasite smashed or even with mixed samples could be detected and the PCR products were predicted as the same as that described above. Thus, D. immiti and D. reconditum could be differentially diagnosed by this specific PCR. Seventeen clinical cases were evaluated and all of them were correctly identified. In this study, ITS1-5.8S-ITS2 of D. immiti or D. reconditum were the first time sequenced and analyzed. No significant similarity of ITS1 and ITS2 between D. immiti and D. reconditum could be observed.

Protective immunity induced by irradiated third-stage larvae of the filaria Acanthocheilonema viteae is directed against challenge third-stage larvae before molting

Jirds (Meriones unguiculatus) were vaccinated with irradiated L3 third-stage larvae (L3) of Acanthocheilonema viteae, and the time required for killing of the challenge L3 was determined. The number of parasites recovered from vaccinated jirds was reduced to about 10% of the control values on the second day after challenge infection and later on. Histological studies revealed an eosinophil-rich infiltrate containing macrophages, neutrophils, and mast cells in the vicinity of the L3 on day 2 after challenge and destruction of the worms by day 4 after challenge. Ultrastructural studies confirmed these data and showed that eosinophils, macrophages, and mast cells were close to the L3 on day 2 after challenge. Flattening of the eosinophils onto the surface of the worms, degranulation of electron-dense material, and rupture of the L3 surface was observed on day 4 after challenge, followed by invasion of the inner of the worms by phagocytic cells. These data show that immune attack against the challenge L3 in vaccinated jirds is initiated between the first and the second day after challenge and that killing occurs around the fourth day after challenge, before the worms undergo their first molt.

A prevalence survey and risk analysis of filariosis in dogs from the Mt. Vesuvius area of southern Italy

A dog microfilariae prevalence and risk factor survey was conducted in 51 contiguous municipalities of the Mt. Vesuvius area (Campania region, southern Italy) in order to add data to the limited epidemiological information available regarding filarial worms in this zone. Between May 1999 and June 2000, blood samples were collected from 351 asymptomatic dogs. Blood samples were examined using a modified Knott's technique and histochemical staining in order to count and identify microfilariae. The results were subjected to statistical analysis and choroplethic municipal maps (MMs) were drawn by a geographical information system (GIS) software. Microfilariae were detected in 63 of the 351 dogs surveyed, constituting a total filarial prevalence of 17.9%. In particular, 56 dogs (15.9%) showed only microfilariae of Dipetalonema reconditum; three dogs (0.8%) only microfilariae of Dirofilaria repens; two dogs (0.6%) microfilariae of both D. reconditum and D. repens and two dogs (0.6%) microfilariae of both Dirofilaria immitis and D. repens. High D. reconditum prevalence was associated with hunting practice, masculine gender and older dogs. There was also a tendency to find high prevalence in dogs sampled in the afternoon. In conclusion, the presence of microfilariae of D. reconditum in 92% of microfilaraemic dogs indicates that this filarial worm was the predominant filarial species in dogs in the Mt. Vesuvius area. In addition, the general trends of the MMs showed that D. immitis and D. repens were present only in a few municipalities, whereas D. reconditum was widely and homogeneously spread throughout the entire study area.

[Prevalence of canine filariasis by Dirofilaria immitis and Dipetalonema reconditum in Maceió, Alagoas State, Brazil]

A survey on the prevalence of Dirofilaria immitis and Dipetalonema reconditum was conducted in 1,519 dogs from Maceió and two coastal areas in the State of Alagoas, Northeast Brazil, from 1995 to 1999, by testing for microfilariae in blood. All blood samples were from exclusively domiciled dogs with a known history, showing that the infections were autochthonous, confirming transmission of canine filariasis in these areas. In Greater Metropolitan Maceió, 15 (1.3%) microfilaremic dogs were detected with D. immitis and 15 (1,3%) with D. reconditum. In the southern coastal area there was an estimated prevalence of 12.7% for D. immitis. D. immitis and D. reconditum microfilaria were 298.1 micrometer and 249.2 micrometer long and 7.3 micrometer and 4.4 micrometer wide, respectively. A Witness immunotest that detects D. immitis antigen was used to confirm parasitological results and reveal occult dirofilariasis cases. Of the total 6,579 females examined, 8 (0.1%) Culex quinquefasciatus were observed to be naturally infected with D. immitis larvae. These results proved dirofilariasis transmission in Maceió and demonstrated D. reconditum in the same geographic area.

Effects of Bay 44-4400, a new cyclodepsipeptide, on developing stages of filariae (Acanthocheilonema viteae, Brugia malayi, Litomosoides sigmodontis) in the rodent Mastomys coucha

Bay 44-4400 was used as a spot on formulation and administered in single doses of 25 and 100 mg/kg to Acanthocheilonema viteae, Brugia malayi, and Litomosoides sigmodontis infected Mastomys coucha on various dates during prepatency, aiming to affect third stage larvae, fourth stage larvae or preadult worms. Microfilaraemia levels were controlled in comparison to untreated controls until necropsies were performed 100 days p.i. (A. viteae, L. sigmodontis) and 150 days p.i. (B. malayi) to determine the numbers of surviving worms and the condition of intrauterine developing stages. A significant proportion (86-100%) of larval and preadult stages of A. viteae were killed by Bay 44-4400 at a dose of 100 mg/kg. A dose of 25 mg/kg had only insignificant effects on the developing parasites, however, it strongly reduced microfilaraemia levels caused by surviving worms in the early phase of patency. Larval and preadult B. malayi and L. sigmodontis were not killed by Bay 44-4400 to a significant degree. Microfilaraemia developing by surviving parasites was generally and significantly reduced throughout the observation period when treatment was performed to affect the preadult parasites. In the other cases variable results were obtained. Intrauterine early embryonic stages were found to be pathologically altered in worms which had been treated at a preadult stage.

Distribution, prevalence, and relative risk of filariasis in dogs from the State of Washington (1997-1999)

Using antigen capture and filter tests, 6,078 dogs throughout the state of Washington were examined for filariasis between July 1, 1997 and October 31, 1999. In western Washington, 791 males and 901 females examined were outdoors, not on prophylaxis, and had traveled out of the state; 6/791 (0.8%) males and 7/901 (0.8%) females were infected with Dirofilaria immitis (D. immitis), and one (0.1%) male and one (0.1%) female were infected with Dipetalonema reconditum (D. reconditum). There were also 392 males and 362 females examined that were outdoors, not on prophylaxis, and had not traveled out of western Washington. One (0.1%) female was infected with D. immitis, and two (0.5%) males and one (0.2%) female were infected with D. reconditum. In eastern Washington, 707 males and 826 females examined were outdoors, not on prophylaxis, and had traveled out of the state; 9/707 (1.0%) males and 4/826 (0.5%) females were infected with D. immitis, and no D. reconditum was found. There were also 376 males and 412 females examined that were outdoors, not on prophylaxis, and had not traveled out of the state. Three (0.8%) males and three (0.7%) females had D. immitis. One (0.2%) female had D. reconditum. Distribution of D. immitis-infected, nontravel dogs in eastern Washington was only found between 120 degrees and 119 degrees west longitude in the communities of Richland, Moses Lake, Okanogan, and Omak. Enzootic transmission of D. immitis and D. reconditum is occurring in both eastern and western Washington.

Mechanisms underlying the transfer of phosphorylcholine to filarial nematode glycoproteins--a possible role for choline kinase

Phosphorylcholine (PC) is a common constituent of proteins secreted by filarial nematodes. As this substance has been shown to interfere with immune responses, we are interested in designing strategies for blocking its attachment. Towards this end, we are investigating the mechanism of incorporation of PC into filarial molecules and in the present manuscript we describe experiments relating to elucidating the source of PC for attachment. Synthesis of phosphatidylcholine in eukaryotic organisms can occur by a mechanism involving the transfer of PC from CDP-choline to diacylglycerol (the Kennedy pathway). By (i) measuring transfer of radio-isotope labelled PC from CDP-choline to parasite molecules and (ii) employing inhibitors of CDP-choline synthesis, we have investigated whether CDP-choline can act as a source of PC for transfer to ES-62, a major secreted glycoprotein of the rodent filarial nematode Acanthocheilonema viteae. Although we can find no evidence of this, we show that attachment of PC is blocked by hemicholinium-3, an inhibitor of choline kinase, the first enzyme in the Kennedy pathway. Thus, at least the first step in this pathway--phosphorylation of choline, would appear to be necessary for attachment of PC to ES-62.

Development of in vitro screening system for assessment of antifilarial activity of compounds

Evaluation of antifilarial activity of new potential agents in vivo is extremely time consuming and uneconomic. In the present study effort has been made to develop an in vitro screening method using Acanthocheilonema viteae, a subcutaneously dwelling rodent filariid with anaerobic metabolic characteristics like human filariids, W. Bancrofti/Brugia malayi as test parasite. Motility test and tetrazolium (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, MTT) based colorimetric assay were used as parameters in in vitro assay. Results showed that 92.3% of compounds (in vivo active) could be picked up in the in vitro assay when both adults and microfilarae (mf) were used simultaneously. Mf and adult stages separately detected, respectively, 84.6 and 69.2% of in vivo active compounds. The adults and mf separately and both the life stages together exhibited, respectively, 80.0, 50.0 and 80.0% false positive results in the in vitro test with in vivo inactive compounds. It is felt that mf stage when used in in vitro test using motility and MTT assays as parameters would be useful in primary screening of new potential filaricides.

PCR-based amplification of total cDNA with high fidelity and high yield from minute amounts of parasite RNA

cDNA, synthesised from total RNA from Acanthocheilonema viteae, was amplified by PCR with a primer derived from the spliced leader 1 sequence of nematodes and oligo-dT. Due to the great number of side products observed in the reaction, a biotinylated oligo-dT primer was used for cDNA-synthesis and the first cycles of PCR. After binding of the PCR products to streptavidin/paramagnetic particles, the (+)strands of the cDNAs were recovered and reamplified. Analysis of the PCR products obtained revealed the presence of full-length cDNAs of at least 1.7 kbp in size in amplified total cDNA from microfilariae, postinfective L3, and adult worms. The total cDNA, from only 20 ex vivo recovered postinfective L3, was efficiently amplified.

Filariae of raccoons from southeast Georgia

The prevalence of filariae in wild raccoons trapped in southeast Georgia was determined. Examination of blood samples revealed that 74 of 113 raccoons (66%) trapped in 6 southeastern Georgia counties were infected. Seventy-three of these raccoons (65%) were infected with Mansonella llewellyni and this parasite was observed in raccoons from every location examined. Dirofilaria tenuis was found in 22 raccoons (20%) and was observed in only 3 of the 6 counties surveyed. An adult specimen of Acanthocheilonema procyonis was found in the subcutaneous tissues of 1 of 5 necropsied raccoons. This is the first record of filariae in raccoons from Georgia. In addition, Dirofilaria-like larvae were found in Aedes taeniorhyncus mosquitoes collected in Liberty County.

Turnover of microfilariae in small mammals 2. Disintegration of microfilariae (Acanthocheilonema viteae) (Filarioidea: Nematoda) after intravenous injection into the jird, Meriones unguiculatus

After i.v. injection of 305 x 10(3) microfilariae (mf) per animal (50 g) into naive jirds, 50.8% of them could be recovered at autopsy 15 min later. Of these, 65.8% were calculated to be in the peripheral circulating blood (PCB) and were completely intact; 18.6% were recovered by perfusion of the lungs and 13.6% from the liver. In both organs about half the mf were associated with adherent lymphocytes and neutrophils but a few were partly disintegrated. Only 2.6% were recovered from the kidneys and the spleen. In long-term injection experiments using the same inoculum size the autopsy was done 15 min and 1, 3 and 6 weeks post-injection (p.i.) of mf into naive jirds. Throughout the experimental period the density of mf remained more or less constant in the PCB, but 3 weeks p.i. the density in the lungs increased up to 14 times to that in the PCB, whereas in the liver it decreased at the same time to a density similar to that in the PCB. In patent animals with adult worms delivering mf these were distributed as follows: 34.7% were calculated to be in the PCB; 24.4% were obtained by perfusion from the lungs and 22.0% from the liver; the rest were found in the kidneys (16.6%) and spleen (2.3%). In the lungs and the liver about 5/6 were associated with adherent cells, partly disintegrated or as fragments. In view of the fact that very few mf become disintegrated immediately after i.v. injection and also from their extremely long sojourn in the PCB, a low turnover rate of mf is presumed.(ABSTRACT TRUNCATED AT 250 WORDS)

Activity of alpha-anilinobenzyl cyanides and 2-methoxycarbonylamino-1-phenylimidazoles, a new class of antifilarial agents

The activity of alpha-anilinobenzyl cyanides (2a-f), 5-aryl-4,5-dihydro-2-methoxycarbonylamino-1-phenylimidazoles (5a-d) and 2-methoxycarbonylamino-1-phenyl-1,3-diazaspiro[4:5]dec-2-ene (5f) have been tested for their micro- and macrofilaricidal activity against Litomosoides carinii and Acanthocheilonema viteae in rodents. In this test alpha-anilinobenzyl cyanides (2a-b), 5-(4-methoxyphenyl)-4,5-dihydro-2-methoxy-carbonylamino-1-phenylim idazole (5b) and 2-methoxycarbonylamino-1-phenyl-1,3-diazaspiro[4:5]dec-2-ene (5f) were found to possess marked filaricidal activity at doses ranging from 3-100 mg/kg given parenterally or orally for 5 days.

Protective immunity linked with a distinct developmental stage of a filarial parasite

Repeated low dose infections of the jird Meriones unguiculatus, with the filarial parasite Acanthocheilonema viteae cause a substantial reduction of the total worm burden, suggesting a parasite-driven immune mechanism that controls super-infections. Quantitative recovery of parasites from tissues of triple infected jirds reveals that the larvae derived from a subsequent challenge infection are inactivated or severely impaired several days after transmission, precisely during their molt from the L3 to the L4 stage. Moreover, only larvae undergoing the molt from L3 to L4 stages are capable of stimulating an immune response directed against the challenge infection, indicating that protective Ag are produced during the molting period. Consistent with this, inactivated L3 or live L4 do not produce the same effect. In contrast to susceptible animals, immune jirds elicit high serum antibody titers against molting Ag. Indirect fluorescence antibody-binding tests with sera from protected jirds reveal specific labeling of the surface of molting L3 and not other larval stages, implying a stage-specific elimination process. The identification of molting L3 as a natural target for host immune mechanisms, emphasizes the central importance of this larval stage for future efforts aimed toward the development of a filarial vaccine.

Effect of 2,2'-dicarbomethoxylamino-5,5'-dibenzimidazolyl ketone on antioxidant defenses of Acanthocheilonema viteae and its laboratory host Mastomys natalensis

The effect of the macrofilaricidal agent of 2,2'-dicarbomethoxylamino-5,5'-dibenzimidazolyl ketone (C.D.R.I. compound 82/437), on the metabolism of reactive oxygen species (ROs) in Acanthocheilonema viteae and Mastomys natalensis was measured following intraperitoneal administration at therapeutic doses. The recovered worms possessed substantially reduced levels of catalase and glutathione peroxidase (GPx), and thus were less able to detoxify H2O2. Nonetheless, the subcutaneous and adjoining muscle tissues, in which the parasites were lodged, exhibited elevated levels of antioxidant enzymes and reduced glutathione. It is concluded that compound 82/437 kills the filariid by paralysing its H2O2 detoxifying capacity without altering ROs metabolism in the tissue in which the parasite resides. Furthermore, since catalase and GPx of the liver and lungs do not show sign of inhibition, a difference appears to exist in the enzymes of the parasite and the host.

Changes in the surface composition after transmission of Acanthocheilonema viteae third stage larvae into the jird

This study describes the dynamics and the biochemical nature of changes in the surface of the filarial nematode Acanthocheilonema viteae after its transmission into the vertebrate host. Vector-derived third-stage larvae (mL3) were inoculated into naive Meriones unguiculatus and recovered from the tissues at different times post-infection until their moult to fourth-stage larvae (L4). Surface-specific labelling with fluoresceinated lectins revealed that the larvae are covered by a carbohydrate envelope. Although the mL3 envelope was strongly reduced one day after transmission, new surface carbohydrates appeared until the onset of moulting, some of which could also be identified on the surface of L4. In general, surface carbohydrates were partially shed by moving larvae, suggesting a loose association of these components in the epicuticle. The fate of cuticular lipids and proteins of L3 and L4 was monitored by external 125I-labelling and differential extraction of the components. Thin-layer chromatography of surface-labelled lipids revealed only minor changes 1 day after parasite transmission. Afterwards the number of lipids accessible to label decreased further until moulting was complete. Two-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis of surface-labelled proteins showed a consistent surface exposure of mL3 specific proteins until 1 day post-infection. Thereafter, the composition of surface-labelled proteins changed rapidly, resembling that of the L4 as early as several days before moulting. During this period individual differences in the composition of surface proteins were evident.

Dose-dependent recovery of adult Acanthocheilonema viteae (Nematoda: Filarioidea) after single and trickle inoculations in jirds

Increasing single doses of 5, 15, 30, 60 and 90 third-stage Acanthocheilonema viteae larvae per animal were inoculated into jirds. The adult worm load increased steadily, whereas the recovery rate decreased significantly, i.e. the correlation between dose and recovery was negative (rs, -0.90; n = 5; alpha, 0.05). The same inoculation doses were given as trickle inoculations of 5 L3 each (3 x 5, 6 x 5, 12 x 5, 18 x 5) at intervals of 2-6 days throughout the prepatency period. Irrespective of the number of repeated inoculations, a rather constant but low load of 7-10 worms/animal was reached. The recovery rate decreased drastically (rs, -1.0; n = 5). When trickle inoculations were carried out in animals exhibiting patient infections, the superinoculated larvae seemed to be destroyed almost completely; thus, a parasite-host equilibrium was guaranteed in all cases. The immunological background is discussed.

Transplantation into jirds as a method of assessing the viability and reproductive integrity of adult Acanthocheilonema viteae from culture

The reproductive integrity and viability of adult female Acanthocheilonema viteae (syn. Dipetalonema viteae) maintained in culture for relatively long periods were assessed by transplantation into jirds. Worms cultured in chemically defined NI medium for approximately 3-4 wk remained active, but microfilarial release declined to barely detectable levels. Microfilarial production, however, was restored when the worms were transplanted subcutaneously into jirds. When cultured in NI medium beyond 4 wk no restoration of microfilarial production occurred on transplantation, presumably due to irreversible injury to the reproductive system. However, when NI medium was supplemented with fetal bovine serum resumption of microfilarial production occurred in transplanted females that had been in culture for as long as 2 1/2 mo. The addition of serum to NI medium played an important role in maintaining and protecting the functional integrity of the reproductive system.

Apodemus sylvaticus, a new host for Acanthocheilonema viteae (Nematoda: filarioidea)

Susceptibility of Apodemus sylvaticus and A. agrarius to infection with Acanthocheilonema viteae was compared with that of hamsters and jirds. Microfilaremia in A. sylvaticus was first noted on day 52 post-infection (p.i.) and lasted during the course of the study (up to day 150 p.i.). Maximum microfilaremic levels (female worm basis) of A. sylvaticus [mean +/- S.D. (n) = 690 +/- 1288(6)] were considerably higher than those of hamsters [16 +/- 18(6)] and jirds [51 +/- 25(5)]. Adult worm recovery in A. sylvaticus ranged from 2 to 40% of the number of infective larvae inoculated. Worm development in A. sylvaticus resembled that in hamsters and jirds. In contrast, microfilaremia was not detected in, nor adult worms recovered from A. agrarius throughout the study.

Association between circulating antigen and parasite load in a model filarial system, Acanthocheilonema viteae in jirds

Jirds (Meriones libycus) were infected with various numbers of Acanthocheilonema viteae L3 stage parasites. During the course of the ensuing 16 weeks, blood samples were collected at 2 weekly intervals and the amount of the major parasite excretory-secretory product (E-S 62) and antibodies directed against it measured. After 16 weeks, animals were sacrificed and the size of the mature worm burden established. In spite of interaction between E-S 62 and host antibody, a statistically significant relationship was found to exist between the amount of E-S 62 present in the bloodstream and the size of the parasite load. It is suggested that the detectable antigen level is more influenced by the size of the worm burden than the presence of antibody and that antibody is only likely to affect adversely antigen measurement in situations where the amount released is relatively low. Examples of this are early in infection and in low-level infections. These ideas are discussed in relation to the development and assessment of serological assays which attempt to predict parasite burden in human filarial infections.

Immune response to Acanthocheilonema viteae infection in multimammate rats (Mastomys natalensis)

The multimammate rat Mastomys natalensis, when infected with the filarial parasite Acanthocheilonema viteae, develops amicrofilaraemia. Worm recovery and the duration and intensity of microfilaraemia were analysed and related to the humoral and cellular immune responses of the host by using an antibody-dependent cell-mediated cytotoxicity (ADCC) assay towards microfilariae (Mf). Mf were detected in the peripheral blood at 7 weeks post-infection (p.i.), reaching maximum levels by 20 weeks p.i., and then gradually decreasing to undetectable levels during the next 36 weeks. The cytotoxic antibodies appeared around 15-18 weeks p.i., and the serum at 36 weeks p.i. induced 70% cytotoxicity to the Mf in vitro in the presence of host cells. The IgM fraction of the immune serum from amicrofilaraemic Mastomys promoted ADCC to Mf both in vitro and in vivo. Macrophages were more potent in inducing cytotoxic effect than eosinophils and neutrophils. Platelets were ineffective in killing the Mf in the presence of immune serum. IgM antibody cleared the circulating Mf from the blood when given passively to infected Mastomys. The average recovery of adult worms was about 20% of the inoculated larvae. No live females could be recovered 56 weeks p.i. Thus protective immune responses built up over an extended period of time are elicited against the Mf and perhaps even to adults in Mastomys infected with A. viteae.

Effect of ivermectin on filariae of Mastomys natalensis

The efficacy of ivermectin (Iv) was evaluated against four species of filariae, Litomosoides carinii, Acanthocheilonema viteae, Brugia pahangi and Brugia malayi in Mastomys natalensis. Animals with patent infections, induced with L3 larvae, by intravenous (iv) infusion of the respective microfilariae (Mf) (5 x 10(4) Mf per animal) or by intraperitoneal (ip) route (2 x 10(4) Mf per animal) were used in this study. A single dose of Iv (100 micrograms.kg-1) given subcutaneously (sc) to Mastomys infected with L. carinii or A. viteae resulted in the disappearance of microfilaremia within 2 h of treatment. Iv treatment of sc-infected animals with Brugia spp. had no immediate effect on the circulating Mf 60 days post-treatment. In contrast, such treatment of animals infected with Mf by intravenous infusion completely eliminated the larvae of all four species from the circulation. Iv treatment had no significant effect on the Mf of L. carinii, B. pahangi and B. malayi in animals infected by the ip route. However, the drug had dramatic effect in killing the Mf of A. viteae in the peritoneal cavity. Sera from Iv-treated normal or from L. carinii- or A. viteae-infected Mastomys were effective in clearing the circulating Mf of the species when administered to animals with the respective infections. Similar rapid clearance of Mf was seen when the sera were administered to animals infected iv with these larvae. Furthermore, adult females of L. carinii and A. viteae recovered from Mastomys on different days after Iv treatment released smaller numbers of Mf in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Homologous and crossreacting immune response of the jird and cotton rat against microfilariae of Dipetalonema viteae and Litomosoides carinii (Nematoda: Filarioidea)

Consecutive injections of microfilariae of L. carinii and D. viteae were carried out in the homologous or heterologous sequence into the corresponding natural or into the experimental hosts. Microfilariae of D. viteae are imunogenic in Sigmodon specifically and crossreacting as well. However, in the natural host, Meriones, they are doubtlessly tolerogenic. The sojourn and level of microfilaraemia are prolonged resp. higher when living D. viteae-Mf are injected s.c. followed by an i.v. injection. However, freeze-killed microfilariae of D. viteae are immunogenic in Meriones. Obviously the two filarial worms living in small mammals realize the balance with their natural hosts in quite a different manner. Which one of the two possibilities, or if one of them at all, reflects the relationship in human pathogenic filariae remains open.

[Dipetalonema dracunculoides (Cobbold, 1870) (Nematoda: Onchocercidae) in an imported dog]

Dipetalonema dracunculoides was found in the abdominal and thoracic cavities of an imported dog.

Dipetalonema viteae and Brugia pahangi transplant infections in gerbils for use in antifilarial screening

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(-8)M ivermectin and milbemycin D had prevented migration; CGP6140, amoscanate, suramin, flubendazole and furapyrimidone were also detected at less than 10(-6)M 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.

Fecundity and localization of Dipetalonema viteae (Nematoda, Filarioidea) in the jird Meriones unguiculatus

In quantitatively infected Meriones unguiculatus autopsied during prepatency, the embryonic development of fertilized eggs in the uteri of female Dipetalonema viteae commenced 29-32 days p.i., and approximately 20 days later the first microfilariae were released. In host animals examined at the onset of patency 45-59 days p.i. the average adult recovery rate was 31%. The worms were localized in the subcutaneous tissue (65.3%), fasciae of muscles (26.9%) and body cavities (7.8%). Female worms from the peritoneal and pleural cavities were significantly longer (44.3 +/- 10.4 mm) than those from the other habitats (33.7 +/- 5.5 mm). Female worms 14-20 weeks p.i. contained a total of 172,700 +/- 62,400 intrauterine stages, 21% of them pathologically altered. Based on these parameters, the expected in vivo fecundity of a female worm was calculated as about 7000 microfilariae per day.

[A 5th filaria of the genus Dipetalonema, parasite of South American monkeys]

Description of D. freitasi n. sp., a parasite of Cebus capucinus: this species, close to D. caudispina, is distinguished by the slightly more complex structure of the vagina and right spicule, the lack of area rugosa on the tail and by the shorter microfilaria. Additional morphological data on the male of D. robini Petit et al., 1985 are given. A comparative table of 4 principal evolutive characters of the genus Dipetalonema (vagina, left and right spicules, epithelio-muscular body wall) is given. D. caudispina and D. freitasi n. sp. represent a small primitive group opposed to the more evolved one made up of D. robini, D. gracile and D. graciliformis.

Longevity of microfilariae following removal of the adult worms

The present study was undertaken to determine the longevity of a population of microfilariae in a natural host following the removal of the adult worms without drug intervention. Four squirrel monkeys previously infected with Dipetalonema gracile were allowed to develop stable microfilaremias. All adult worms were then removed surgically from the peritoneal cavity. Weekly microfilaria counts were made on each animal and the decline in microfilariae recorded. At the time of adult worm removal, microfilaremias ranged from 750 to 12,500 mf/ml. The observed decline in microfilaria densities was gradual, but steady, in all animals. Microfilariae persisted in 1-ml blood samples for 60, 62, 91, and 101 weeks following removal of adult worms. The results indicate clearly that in a naturally produced population, in a natural definitive host, microfilariae survive for 60 to 100 weeks. The gradual decrease in microfilarial densities would appear to be the result of the death of specific batches or broods of microfilariae. The microfilariae which persisted in the blood the longest undoubtedly represent those which were produced just prior to the removal of the adult worms. It is postulated that because of the long life-span of microfilariae, female worms are not called upon to produce a continual supply of microfilariae, nor is the need for mating as frequent as might be expected. Equally important, the number of microfilariae which the host is called upon to phagocytize is considerably smaller than previously suggested.

Protective immune responses of the jird to larval Dipetalonema viteae

In vivo and in vitro experiments were performed to study immune protective mechanisms against larval Dipetalonema viteae. Jirds infected with 30 third-stage larvae (L3) of D. viteae for 1, 3 or 5 weeks showed significant killing of challenge larvae implanted for 2 weeks in diffusion chambers. A retardation of larval growth was seen 7 days after larval implantation, and larval death was observed beginning at 10 days. When L3 were placed in vitro with peritoneal exudate cells (PEC) from normal jirds, cellular adherence was seen starting on Day 4, and larval death was seen on Day 10. It was concluded that larvae had to undergo some development in vitro, that would allow cellular adherence to larval surface. Larvae, recovered after 7 days in vivo or in vitro, were placed in culture with normal PEC; cell adherence and worm death occurred at equal rates for both groups of worms. Larvae which had been in culture for 7 days were implanted in immunized jirds for 7 days. Significant killing of these worms was observed, whereas larvae recovered from ticks prior to implantation were not killed. In vivo and in vitro results therefore show that larval development is required for generating susceptibility to specific and/or non-specific immune reactions. A hypothesis is suggested for the function of larval retardation.

Transplanted Dipetalonema viteae in the jird: effect of worm burden on parturition rates and microfilaremia

Dipetalonema viteae was studied in the jird, Meriones unguiculatus, to determine the mechanism controlling the level of peripheral microfilaremia. Jirds killed 40 days after infection served as donors of female worms of known age and reproductive status. These worms were transplanted into uninfected jirds and the resultant microfilaremias were monitored. After approximately 100 days, the recipient jirds were killed and 58% of the transplanted worms were recovered alive but depleted of sperm and microfilariae, regardless of the total number implanted in a given host. A direct linear relationship between microfilaremia and the number of recovered adult worms was found. Based on the uniform absence of sperm and microfilariae in the recovered worms it was concluded that female worms, under the conditions of the present study, do not control the peripheral microfilaremia in multi-worm infections through a reduced parturition rate.

Soleus muscle adenosine-5'-triphosphate (ATP) levels in Mastomys natalensis with Dipetalonema viteae infections: effect of diethylcarbamazine

Adenosine-5'-triphosphate (ATP) levels in the soleus muscles of Mastomys natalensis during the patent phase of Dipetalonema viteae infection were studied. Decreased ATP levels were found in the infected animals as compared with the uninfected controls. Diethylcarbamazine citrate produced an 'anaphylactic reaction' and enhanced microfilaraemia in the infected animals, but did not cause any lowering of the soleus muscle ATP in the infected as well as in the uninfected animals.

Retinol deficiency and Dipetalonema viteae infection in the hamster

Following chronic retinol (vitamin A) deprivation leading to exhaustion of liver vitamin A reserves below 50 I.U. per liver hamsters were fed diets either deficient in ("Rd":250 I.U.A./kg in experiment I, 1000 I.U.A/kg in experiment II) or enriched with retinol ("Rw":10000 I.U.A/kg in experiment I and II). After 4 weeks some of the animals (36 in experiment I, 30 in II) were infected with 150 3rd-stage larvae of D. viteae, while clean animals were kept as controls. The retinol status, the immune response (indirect fluorescent antibody test: IFAT) and parasitological parameters were examined up to 8 (experiment I) and 12 weeks (experiment II) post infection (p.i.). Rd hamsters had levelling off of weight gain or weight loss, severely deficient retinol levels in serum and liver, and high mortality. Weight gain was less in infected than in uninfected hamsters, and the capacity of infected Rw animals to restore liver retinol was significantly lower than that of uninfected Rw animals. IFAT titres were similar in Rd and in Rw animals, but microfilaraemia was significantly enhanced at 8 and 10.5 weeks p.i. in Rd hamsters. While the number of worms recovered from Rd and Rw hamsters was similar, there was a significant increase in the ratio of female to male worms in Rd hamsters. Rd hamsters in experiment I produced 3.3 times the worm mass per 100 g body-weight than Rw hamsters. Also, the average mass per female worm was significantly higher in Rd than Rw in hamsters, and this parameter was negatively correlated with the liver retinol concentration in experiment I(r = -0.89). Retinol deficiency has a marked effect on growth and fertility of D. viteae in hamsters.

Studies of potential filaricides: Part 14--Activity of 1-iso-butoxycarbonyl-4-methylpiperazine against experimental filariasis

The synthesis and filaricidal activity of 1-iso-butoxycarbonyl-4-methylpiperazine against Litomosoides carinii in Sigmodon hispidus and Dipetalonema viteae in Mastomys natalensis is reported. At an intraperitoneal or oral dose of 3 mg/kg given for 6 days, the compound removed 91% of the circulating microfilariae but had no effect on adult L. carinii. However, it killed all microfilariae and adults of D. viteae at a subcutaneous dose of 50 mg/kg given for 6 days. The compound also possessed chemoprophylactic activity against the larvae of L. carinii and D. viteae at a dose of 30 and 50 mg/kg respectively.

Separation of viable microfilariae free of blood cells on Percoll gradients

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

[Effect of 17 beta-estradiol, progesterone and testosterone on Dipetalonema vitae parasitosis in the castrated female golden hamster Cricetus auratus]

In Dipetalonema viteae filariasis of Cricetus auratus, it seems that the natural estrogenic hormon, the 17 beta-estradiol as well as the progesterone have a part in the protection observed in the females.

Filaricidal effects of Cyclosporin-A against Dipetalonema viteae in Mastomys natalensis

Outbred male Mastomys natalensis were injected subcutaneously with 100 infective larvae of Dipetalonema viteae obtained from Ornithodorus tartakovskyi. Groups of five animals were treated with 30 mg/kg of the immunosuppressive drug Cyclosporin-A daily for five days (experimental) or Miglyol 812 (control). One group served as untreated controls. Contrary to expectations, 60% of the animals were completely protected against D. viteae and the remainder were partially protected. The mechanism remains unknown.

Immunocytochemical studies on several developmental stages of Dipetalonema viteae (Filarioidea)

The binding of antibodies to infective larvae (L3), eggs, uterine contents and blood microfilariae was demonstrated by light microscopy employing the peroxidase-antiperoxidase (PAP) method. Antigen-antibody reactions were located on the shell of filarial eggs as well as on the cuticle and the interior of L3 and microfilariae. Using sera from Meriones unguiculatus, Mastomys natalensis and golden hamsters infected with D. viteae obtained at 7, 14, 21 and 28 weeks p.i. it was observed that the intensity of the immunostaining on several developmental stages of the filariae decreased with increasing duration of infection. This effect was more pronounced in the case of M. unguiculatus and M. natalensis than in the case of golden hamsters. For detection of surface antigenicity the simple procedure of drying the test material on microscopic slides proved to be time saving and equally specific as compared to the embedding in Epon of the filarial stages and the successive preparation of semithin sections. However, embedded filarial stages presented more intensive immunostaining than nonembedded stages. Moreover, sections allowed to demonstrate antigen-antibody reactions on the cuticle as well as inside the body cavity of the stages.

Complement-mediated leukocyte adherence to infective larvae of Dipetalonema viteae (Filarioidea): requirement for eosinophils or eosinophil products in effecting macrophage adherence

The present study reports the existence of C-mediated adherence of eosinophils and/or macrophages to filarial infective larvae of Dipetalonema viteae. C3 molecules are present on the surface of the parasite, as shown by immunofluorescence studies. Samples of fNRS depleted of AP of complement by treatment with Zymosan A or of factor B by heating at 50 degrees C for 20 min fail to mediate cell adherence to the parasite. In contrast, fNRS inactivated for CP of complement by the chelating agent EGTA retains its activity in mediating cell adherence to the parasite. There is a significant consumption of factor B and AP of complement when infective larvae are incubated in fNHS. Consumption of C4 of the CP of complement is much lower in the same test. The adherence of macrophages cannot occur without the simultaneous presence of eosinophils, whereas eosinophils probably act alone and not in concert with macrophages. The eosinophil adherence is associated with degranulation. The damage is notably enhanced by replacing the spent eosinophil population with a newly obtained population. In the present test system, mast cells did not adhere to filarial larvae even when mast cell-rich populations were used, nor did they effect macrophage adherence when presented in association with the latter. When eosinophil-enriched cell populations containing less than 1% mast cells were used, cell adherence to filarial larvae still occurred, but the presence of 30% mast cells in such cell populations markedly increased both the rate and level of adherence. We suggest that a cell-mediated adherence and destruction dependent upon the activation of complement via AP, without a requirement for specific antibody, may represent a natural mechanism of parasite killing in a nonimmune host.