Filaricidal properties of a wild herb, Andrographis paniculata

Water decoction of the leaves of Andrographis paniculata killed in vitro the microfilaria of Dipetalonema reconditum in 40 min. Three subcutaneous injections of the extract into infected dogs at 0.06 ml per kg body-weight reduced the number of microfilariae in blood by more than 85%. The larvae were not totally eliminated with more infections but the reduced microfilarial level persisted. No toxic effect of the extract was observed in rabbits. The treated dogs became lethargic initially for a week, probably due to the mass killing of microfilariae.

Peripheral localisation of an IgE immune response at axillary lymph nodes draining the site of a local parasitic infection

Wistar-Furth rats were infected subcutaneously with L3 larvae of Dipetalonema viteae, filaria of Meriones libycus. Lymph nodes draining the site of immunization contained numerous IgE-staining cells identified as lymphoid cells. In other lymphoid tissues, IgE-staining cells were rare. They were absent in the lamina propria of the small intestine. These data support the view that IgE lymphoid precursors are present in peripheral lymph nodes.

Electron microscopic studies on microfilariae of Dipetalonema viteae and Litomosoides carinii: the occurrence of intracellular parasites after treatment with metrifonate or diethylcarbamazine

Microfilariae of Dipetalonema viteae and Litomosoides carinii were studied by means of electron microscopy after oral treatment of their hosts with metrifonate (3 x 100 mg/kg) or diethylcarbamazine (3 x 250 mg/kg). These dosages led to the disappearance of microfilariae from the peripheral venous blood. However, in numerous organs blood capillaries or interstitial spaces contained degenerating microfilariae. In these cases the cytoplasm of the microfilarian cells was completely lysed, whereas the cuticle seemed to be unaffected, at least initially. Microfilariae of both species were also often found intracellularly especially in liver and muscle cells after application of both drugs. The intracellular microfilariae, however, had fewer or even no lesions, suggesting that they might escape the activity of the drug.

Courses of infections with Plasmodium falciparum in own monkeys displaying a microfilaremia

Infections with the Uganda Palo Alto, Malayan Camp-CH/Q, Vietnam Oak Knoll, and Vietnam Smith strains of Plasmodium falciparum in owl monkeys (Aotus trivirgatus griseimembra) with concomitant microfilaremias usually, but not always, followed a more benign course than infections with the same strains in monkeys free of filarial infections. Four distinct microfilariae were identified in systematic examinations of 26 monkeys, 5 with self-limited infections with P. falciparum, 9 with normally benign self-limited infections with P. vivax, and 12 without previous malaria. The microfilariae found included: Dipetalonema (Dipetalonema) gracile, Tetrapetalonema (Tetrapetalonema) barbascalensis, T. (T.) panamensis, and an unidentified species designated "Aotus C." Among 23 monkeys studied completely, 14 were infected with a single species, 4 had double infections, and 5 had triple infections. T. barbascalensis was identified in 16 monkeys, T. panamensis in 11. Although data were very limited, there was a suggestion that infections with P. falciparum were less intense in monkeys infected with T. barbascalensis, either alone or with other filariae, than in subjects infected only with T. panamensis.

Miniature anion-exchange/centrifugation technique for the diagnosis of microfilaraemia in the field

The miniature anion-exchange/centrifugation (AEC) technique, developed originally for the detection of low parasitaemias in laboratory rodents, was adapted to field use for the diagnosis of trypanosomiasis in man in Africa and was tested in The Gambia. During this field study it was found that microfilariae of Dipetalonema perstans could also pass through the anion exchange column and appear in the centrifugate as 'medusa heads'. One locality-group (Mansafa Bolon) showed a generally higher prevalence and prevalences in women over 40 years old were higher than in the corresponding male groups in every locality. The potential usefulness of this technique in epidemiological studies of filariasis and ways of improving the accuracy of numerical estimates are briefly discussed.

Serum IgE levels in rats infected with Dipetalonema viteae L3 larvae

Serum IgE levels were measured by radioimmunoassay in rats infected with various doses of L3 infective stage larvae of Dipetalonema viteae. A high stimulation in total serum IgE levels was found with minute doses as well as with large doses of parasite, and IgE levels remained elevated for several months. No further increase in IgE levels was induced by a secondary infection.

[Simultaneous infection of Mastomys natalensis with Dipetalonema witei and Litomosoides carinii (author's transl)]

Mastomys natalensis that has been described by Lämmler et al. (1968) as suitable host for Litomosoides carinii can also serve as final host for Dipetalonema witei. At the end of the prepatency period the microfilaraemia increased as rapidly in Mastomys as in the original final host Meriones persicus. Maximal microfilaraemia was observed earlier in Mastomys (120 days p.inf.) than in Meriones (250 days p.inf.). Accordingly microfilariae counts decreased more rapidly in Mastomys. The maximal counts found in Mastomys was 78000 microfilariae/ml blood, which is 3.2 times less than in M. persicus. Furthermore it could be demonstrated that a simultaneous experimental infection of Mastomys with D. witei and L. carinii in possible. The course of microfilaraemia and the number of macrofilariae were comparable in mono- and simultaneous infections for both species of filariae. The macrofilariae of D. witei began to die earlier than those of L. carinii both in mono- and in simultaneous infections. The percentage of dead macrofilariae was 3.8% 110 days p.inf., and 13.1% 130 days p.inf. respectively. Therefore, chemotherapeutic experiments should be terminated and evaluated about 110 days p.inf.

Studies on Dipetalonema viteae (Filarioidea). 4. Passive transfer of immunity to circulating microfilariae by spleen cells

Passive transfer experiments provided clear evidence for a role of spleen cells in the immunity of hamsters against Dipetalonema viteae microfilariae. 106 or more spleen cells from postpatent (amicrofilaraemic) hamsters suppressed incipient microfilaraemia in syngeneic recipients when transferred at either week 2 or week 6 of a primary infection. Spleen cells from microfilaraemic donors (week 15-16 post infection) were also capable of transferring immunity against microfilariae. The spleen cell transfer never affected the survival of adult worms. After transfer of spleen cells from either patent or postpatent hamsters, antibodies to the cuticle of microfilariae could be found in the sera of recipients as early as week 8 of a primary infection.

[Influence of the sex of the final host on experimental Dipetalonema vitae filariosis in golden hamsters Cricetus auratus (author's transl)]

The authors have studied the influence of the sex of the host on experimental Dipetalonema viteae parasitosis in golden hamsters Cricetus auratus. The parasited hamsters are sacrificed fifteen days after testing for microfilarial count, and then the extent of the infestation is measured by counting the number of male worms and female worms. The average level of microfilarial count is significantly higher in male hamsters than in female hamsters. The same applies to the extent of parasitism: the average number of adult worms is higher when parasitosis occurs in males. However, the sex of the hamster has no influence on the proportion of male and female worms present and the degree of microfilarial count, observed in male hamsters seems to result only from the presence in the same of a greater number of worms.

On Dipetalonema viteae infection of Mastomys natalensis

Experimental infections were carried out with the tissue-dwelling filaria Dipetalonema viteae using the argasid tick Ornithodorus moubata as the intermediate and the multimammate rat Mastomys natalensis (Strain GRA Giessen) as the final host. The optimum infective dose was found to be 50 third-stage larvae, which produced patent infections and the recovery rates of adult parasites were 47.6 and 26.4% of the inoculated larvae 140 and 189 days after infection, respectively. After an average prepatent period of 57 days, the microfilaraemia increased progressively and reached relatively low maximum values about 192 days after infection. These maximum values were followed by rapid decrease of microfilaraemia, but microfilariae were still detectable at 261 days post infection. Following the subcutaneous injection of infected animals with dexamethasone in single doses each of 1, 10 or 20 mg/kg body weight 30 minutes before blood puncture, a dose-dependent increase in the microfilarial counts in the circulating blood was observed, this reaching maximum values between 120 and 160 days after infection. Repeated administration of single doses of 10 mg/kg dexamethasone revealed an uniform but temporary increase in the microfilaraemia but this was not associated with any alterations in the reproductive organs of adult female parasites. No correlation could be found between the number of microfilariae in the circulating blood and the number of adult worms recovered from the subcutaneous connective tissue. At necropsy 300 days after infection living female parasites could not be found any more.

Kinetics of Dipetalonema viteae infections established by surgical implantation of adult worms into hamsters

Native LVG strain hamsters were infected with Dipetalonema viteae by the surgical implantation of adult worms. Groups of hamsters received either 50 male, 50 female, 50 male plus 50 female or 25 male plus 25 female worms per hamster. Approximately 50% of the transferred worms became established in the recipient hosts regardless of the number or sex of the worms implanted. Microfilaremia occurred in recipient hamsters within 1 week after the transfer of female or male plus female worms. This microfilaremia became negative on week 9 post-transfer and no microfilaremia developed in these hamsters following a secondary challenge infection of male plus female worms. Hamsters whose primary infection consisted solely of male worms developed a microfilaremia when challenged with male plus female worms.

Recovery of intact male and female Dipetalonema streptocerca from man

When attempts at teasing adult Dipetalonema streptocerca free from biopsy specimens of human skin proved futile a digestion procedure was initiated. Punch biopsy specimens fixed in Michel's solution (ammonium sulfate) were incubated at 25 degrees C for 3 days in a 1.0% solution of collagenase in tris-HCl buffer. Intact worms were carefully teased out of the digested collagen and camera lucida drawings and measurements were then possible. This marks the first description of intact D. streptocerca adults recovered from man.

High Dipetalonema reconditum microfilarial counts in two dogs

Dipetalonema reconditum microfilarial counts of 509 and 932/ml of blood, respectively, were found in 2 dogs thought to have been infected with Dirofilaria immitis. The high counts were attributed to a state of immunosuppression. It was concluded that microfilarial width is a more reliable criterion that microfilarial numbers for the differentiation of D immitis and D reconditum infections. For reliable width measurements, it is necessary to use the modified Knott or polycarbonate filter techniques, inasmuch as the cellulose filter technique gives misleading results.

Studies on Dipetalonema viteae (Filarioidea) I. Microfilaraemia in hamsters in relation to worm burden and humoral immune response

The course of a primary infection with Dipetalonema viteae was studied in one randomly bred and in one inbred strain of hamster. Worm recovery and the duration and intensity of the microfilaraemia were analyzed and related to the humoral immune response of the host by using the indirect immunofluorescent antibody test on frozen sections of female worms, on eggs and on intact microfilariae. The inbred strain showed a greater susceptibility to the parasite. This was evidenced by high worm recovery and prolonged microfilaraemia. The duration of microfilaraemia did not depend on the number of recovered female worms. Most of the randomly bred hamsters suppressed microfilaraemia by week 30 post infection whereas some hamsters of the inbred strain were still microfilaraemic. Splenectomy prior to infection did not affect the duration of microfilaraemia. Antibodies to the cuticle of microfilariae always appeared in the sera after immunity to circulating microfilariae had been built up.

Studies on Dipetalonema vitae (Filarioidea). II. Antibody dependent adhesion of peritoneal exudate cells to microfilariae in vitro

Peritoneal exudate cells from normal uninfected hamsters adhered in vitro to microfilariae in the presence of 19S antibody fractions from hamsters which had suppressed or were going to suppress their microfilaremia. The adhering cells were predominantly mononuclear, although eosinophils were occasionally found. Experiments with sensitized microfilariae and peritoneal exudate cells indicated that the macrophage probably recognizes the microfilariae/antibody complex. Macrophage cytophilic antibodies did not seem to be involved. This adhesion reaction may initiate the trapping of microfilariae in vivo, thus contributing to the observed acquired immunity to circulating microfilariae in the hamster.

Studies on naturally occurring filarial infections in dogs in Lebanon. I. Dipetalonema reconditum

A survey for filarial parasites was carried out on dogs in Lebanon. The peripheral blood was examined for microfilariae and the skins and carcasses for adult worms. Three methods were used for blood examination: (a) thick blood films stained with Giemsa; (b) a modified Knott's technique (Methylene Blue stained); (c) sodium citrate technique. Two species of filarial worm were found, Dipetalonema reconditum and another species of Dipetalonema which will be described in a later paper. The morphology of microfilariae and adults of D. reconditum is described. The microfilariae of D. reconditum showed a nocturnal sub-periodicity. Attempts were made to find vectors by feeding Aedes aegypti, Aedes phoeniciae, Culex pipiens molestus and Clenocephalides felis on an infected dog. Developing and infective stages were recovered only from C. felis.

Dipetalonema viteae infection in hamsters: enhancement and suppression of microfilaraemia

Mature male Dipetalonema viteae released a substance(s) which caused enhanced microfilaraemia in infected hamsters. In hamsters implanted with female D. viteae, the microfilaraemia of a subsequent infection was suppressed. The microfilaraemia of female worms implanted in hamsters was depressed within 5 days when the animals were given a further infection with infective larvae.

Dipetalonema viteae in hamsters: effect of antiserum or immunization with parasite extracts on production of microfilariae

After hamsters have been infected with Dipetalonema viteae for about 4 months, microfilariae disappear from the circulation but the adult worms remain alive and active. Such hamsters are said to harbour a ‘latent’ infection. Additional adult worms implanted into such hamsters produce no microfilariae, but adult worms recovered from hamsters with latent infections resume microfilariae production when surgically transplanted into new hosts. In vitro, worms from hamsters with latent infections renewed microfilariae production in the presence of serum from uninfected but not infected hamsters. Serum from infected animals had a marked suppressive effect on the microfilariae production of adult worms implanted into passively immunized hamsters. This suggests that microfilarial release is regulated by a serum factor. Microfilarial production in in vitro and in vivo experiments was more strongly inhibited by serum taken from hamsters with latent infections and hamsters infected for only 30 days (pre-patent) than by serum taken 90 days after infection (whilst microfilariae were in the circulation of the serum donors). A cytotoxic effect of sera from infected hamsters on the microfilariae could not be demonstrated.

In animals immunized by extracts of adult worms or microfilariae, microfilaraemia was considerably reduced. In contrast, animals immunized repeatedly with the extract from small numbers of microfilariae during the pre-patent phase of an infection had an enhanced microfilaraemia. Adult worm numbers were not affected by immunization except in animals given extract from a single female worm which harboured fewer worms than controls.

Streptocerciasis: observation of adult male Dipetalonema streptocerca in man

In 75 biopsy specimens of skin from 34 patients with streptocerciasis who had been treated with diethylcarbamazine, we found 39 female and six male adult Dipetalonema streptocerca in the dermal collagen. This is the first report of adult male D. streptocerca in man, and identifying features are described.

[Deviation of the life cycle of Dipetalonema viteae (Filarioidea)]

Dipetalonema viteae is a filarial that can evoluate among hosts zoologically broadly apart (Ixodides and Argasides), but always gathered from meriones burrows. Its evolution is, on the contrary, blocked among most of the other ticks, particularly among Ornithodoros erraticus morphologically very similar to the normal vector. Our work concerns the experimental deviation of the cycle of Dipetalonema viteae, with its possible adaptability in the bosom of an intermediate of fowl tropism and a permanent host, different from a gnawing.

Studies on the diagnosis and treatment of human filariasis in Rhodesia

Experiences in Rhodesia with various recovery techniques available for the laboratory diagnosis of infections with Dipetalonema perstans and Wuchereria bancrofti are discussed. A diagnostic laboratory regimen for routine filarial investigations is suggested. Included are preliminary observations on the use of mebendazole (Vermox) for the treatment of D. perstans infections.

Cryopreservation of infective larvae of Dipetalonema viteae

infective larvae of Dipetalonema viteae produced infections in Mongolian jirds (Meriones unguiculatus) after storage of infected ticks (Ornithodoros tartakovskyi) in the presence of dimethyl sulfoxide (DMSO, 5%) for 7 or 595 days in liquid nitrogen (-196 C). Infectivity of these larvae was only partially impaired. Microfilaremias of test jirds were generally lower than those of control jirds given nonfrozen larvae; however, the majority of test jirds developed microfilarial counts suitable for use in infecting ticks. In contradistinction, larvae frozen free of the tick failed to retain infectivity. Apparently the tick, in conjunction with DMSO, protects the larvae during freezing and thawing.