Ivermectin prophylaxis against experimental Onchocerca volvulus infection in chimpanzees

Ivermectin was tested for possible prophylactic action against the third and fourth larval stages (L3 and L4) of Onchocerca volvulus inoculated into chimpanzees. The infective larvae (L3) were obtained from laboratory-raised black flies. Eighteen chimpanzees were inoculated, each with approximately 250 L3. Six were treated with ivermectin (200 micrograms/kg) on the day of inoculation, 6 were treated with ivermectin on day 28, and 6 were not treated. Monthly skin snips were taken for the next 30 months to detect patent infection. One of the chimpanzees treated with ivermectin on the day of infection developed a patent infection as did 4 of the 6 treated at day 28 and 4 of the 6 control animals. The results suggest that ivermectin may have a partial in vivo effect against the L3 of O. volvulus but has no effect against later larval stages of the parasite.     

Diagnosing multiple parasitic infections: trypanosomiasis, loiasis and schistosomiasis in a single case.

A case is reported of a 32-year-old traveller with loiasis, schistosomiasis and African trypanosomiasis. The patient had been working in oil exploration in Nigeria and Gabon and presented with Calabar swellings and carpal tunnel syndrome. Serology for all 3 diseases was positive but microfilariae of Loa loa and ova of schistosomiasis were not found. Treatment with diethylcarbamazine and praziquantel was given for loiasis and schistosomiasis respectively. Trypanosomes were isolated from a lymph node aspirate only after repetition of the procedure 2 months later and the patient was treated with suramin. He developed a drug induced nephritis and was then treated successfully with alpha-difluoromethylornithine. There is a discussion of the difficulties encountered making these diagnoses in Europeans particularly where there are atypical clinical features. The risks of rural work in West Africa are noted and the importance of considering all parasitic diseases relevant to the travel/occupational history is emphasised.     

Ivermectin: concentration-dependent effects on adenosine triphosphatases in adult worms of Onchocerca volvulus

The effect of increasing concentrations of ivermectin on adenosine triphosphatase (ATPase) activity was investigated in adult worms of Onchocerca volvulus. Mean Mg- and Na,K-ATPase activities decreased significantly (F ratio = 29.82, P < 0.01 and F ratio = 28.54, P < 0.01, respectively) with increasing concentrations of ivermectin (0-100 ng/ml) in the female worms. When male and female worms were mixed with equal amounts of proteins from each, only the Na,K-ATPase activity was significantly decreased (F ratio = 56.61, P < 0.01) over a similar range of ivermectin concentrations. Since ivermectin exhibits concentration-dependent effects on both ATPases in female adult worms, this might provide an insight into other effects of the drug. However, the adjustment of the dose of ivermectin to obtain a nodular concentration of at least 40 ng/ml is therefore recommended in the complete chemotherapy of onchocerciasis.     

Ivermectin: reduction in prevalence and infection intensity of Onchocerca volvulus following biannual treatments in five Guatemalan communities.

Residents of five hyperendemic communities located in the central focus of onchocerciasis in Guatemala were treated with ivermectin (Mectizan) or placebo every six months for 30 months. The effects of treatment on prevalence and the intensity of skin infection (microfilarial skin density [MFD]) were evaluated. Significant and persistent reductions in both of these indices were achieved by coverage of 80.7% of the eligible populations. The highest proportionate reductions in both indicators of infection occurred after the first treatment, followed by more gradual decreases through the fourth treatment. In one community in which the mean coverage was 92.7%, prevalence decreased from 74.0% at pretreatment to 34.9% after four treatments, while the MFD decreased from 7.8 to 2.0; reductions of 52.8% and 74.3% from pretreatment values, respectively. In every ivermectin-treated community except one, in which drug acceptance was low, the mean community MFD values were reduced to the level associated with low infectiousness for the vector, Simulium ochraceum. Moreover, the category of MFD associated with high vector infectiousness was reduced at least ten-fold over the pretreatment level. One community had low participation during the first two treatments (32.8% and 22.7% of those eligible). This increased to 55.2% at the third treatment because of implementation of an educational program describing both the disease and the beneficial effects of ivermectin and because skin biopsies and nodulectomies were not performed. Secondary reaction rates for all communities were 29.5%, 9.9%, 10.3%, 8.2%, and 7.1% for the first through fifth treatments, respectively. Pruritus was the most common (34.0%) secondary reaction, followed by facial edema (31.8%). All reactions were classified as mild to moderate. Recommendations for mass distribution of ivermectin in Guatemala are given.     

HIV infections in northwestern Cameroon: identification of HIV type 1 group O and dual HIV type 1 group M and group O infections

HIV-1 strain diversity was examined in a study population that consisted of hospital and clinic patients from seven cities and villages located in the northwestern regions of Cameroon. Specimens were screened using a serological algorithm designed to identify HIV-1 group M, N, and O, and SIVcpz-like infections followed by RT-PCR amplification to characterize the infecting virus. The results show that the HIV epidemic in northwest Cameroon is dominated by HIV-1 group M CRF02_AG infections (57%). Additional group M subtypes present include A, D, F2, G, and CRF01_AE. Based on discordant subtype classification between gag and env sequences, a high percentage (23%) of viral strains appear to be unique intersubtype recombinants with the majority (88%) involving recombination with CRF02_AG. Group O prevalence is low accounting for only 0.4% of HIV infections. However, group O strain diversity is high; isolates from clades I, IV, and V, as well as unclassified and recombinant strains, were found. Three dual infections by HIV-1 group M and group O were identified and characterized. In two specimens, both group M and O sequences were amplified in gag, pol, and env suggesting the presence of both viruses. Analysis of the third specimen shows the presence of a group O virus and an intergroup M/O recombinant virus. Finally, no infections due to HIV-1 group N or SIVcpz-like strains were found in the study population.     

Population dynamics of Loa loa and Mansonella perstans infections in individuals living in an endemic area of the Congo.

A follow-up of Loa loa and Mansonella perstans microfilaremia was carried out in an adult population living in a highly endemic area of the Congo. Infection rates and parasite loads were found to be stable in the general population, both in the short-term (two months) and long-term (3-4 years) followup. The microfilarial status of most of the subjects examined did not change between tests. At the individual level, the microfilarial densities of L. loa and M. perstans also remained remarkably constant over time. This results in a qualitative and quantitative stability of the parasitic material available for the vectors.     

Albendazole in the treatment of opisthorchiasis and concomitant intestinal helminthic infections

A total of 52 adult patients with opisthorchiasis with or without concomitant intestinal helminthic infections were treated with albendazole at dosage regimens of 400 mg twice daily for 3 days (group I with 25 patients) and 7 days (group II 27 patients). By concentration method with four examinations from two faecal specimens of each patient the cure rates and percentage egg reduction on day 30 in group I and group II were 12% and 33%, 94 and 95 respectively; by Stoll method the cure rates and percentage egg reduction were 40% and 63%, 92 and 92 in group I and group II, respectively. There were no statistically significant differences between the results of the two regimens. Twenty six patients with hookworm and 9 patients with S. stercolaris infections were cured. Opisthorchis viverrini, N. americanus, A. duodenale, A. ceylanicum, E. malayanum, E. ilocanum, S. stercolaris, E. vermicularis, and T. saginata segments were expelled in stools, mostly on days 1 to 4. Most of the patients felt relieved from symptoms of pain in the right hypochondrium and epigastrium. The side effects were mild and transient. There were no evidence of toxic effects on the bone marrow, heart, liver or kidneys. Albendazole was shown to be effective against Opisthorchis viverrini infection as well as other concomitant intestinal helminthic infections; but the optimal dosage and duration of treatment have not yet been achieved.     

Specific and cross-reacting antibodies in human responses to Onchocerca volvulus and Dracunculus medinensis infections

Immunoelectroblotting and enzyme-linked immunosorbent assay were used to identify non-cross-reacting antigenic components of Dracunculus medinensis and the filarial worms Onchocerca volvulus, Loa loa, Wuchereria bancrofti, Brugia malayi, and Mansonella ozzardi. Parasite specific serodiagnostic ELISA systems for onchocerciasis and dracunculiasis were devised based on these findings. Phosphate buffered saline extracts of adult worms were passed through a column of monoclonal antibodies to phosphorylcholine (PC). Crude and PC-depleted extracts were reacted on ELISA plates with individual sera from subjects infected with a range of nematodes. Binding of total antibody (Ig) or IgG class antibody and IgG4 subclass antibody was revealed using goat antihuman-Ig-phosphatase conjugate, or appropriate mouse monoclonal antihuman-Ig-type-specific reagents, followed by goat antimouse-Ig-phosphatase conjugate. Specificity of ELISA was improved by restricting reaction to the host's IgG4 antibody subclass, and/or by removing PC determinants from crude antigens. In parallel immunoelectroblots, crude and PC-depleted extracts probed with pooled sera showed potentially useful diagnostic antigens, including a 12 kDa protein from D. medinensis and 14, 18, and 27 kDa proteins from O. volvulus. Two Onchocerca specific ELISA systems non-reactive with antibodies to D. medinensis were devised.     

Development of onchocerca lienalis and O. volvulus from the third to fourth larval stage in vitro

Third-stage larvae of Onchocerca volvulus and O. lienalis were observed to molt to the fourth stage in various cell-free in vitro systems. The percentage of O. lienalis completing the molt was similar in the three culture media and two gas phases tested ranging from 44.8% (1:1 IMDM:NCTC + 5% CO2: 95% N2) to 56.7% (L-15 + 5% CO2: 95% air). Percent molting in O. volvulus ranged from 0% (F12(K) + 5% CO2: 95% N2) to 33.3% (L-15 + 5% CO2: 95% N2). All media were supplemented with either 20% FCS or 20% horse serum. Molting by O. lienalis occurred on days 2-5 in culture. Molting by O. volvulus was observed as early as day 5 and as late as day 10. Incomplete casting of the third-stage cuticle was frequently observed in O. volvulus. Larvae of both species entered a lethargus 24-48 hours prior to the onset of molting. Maximum survival in culture was 42 days for O. lienalis and 25 days for O. volvulus. Significant growth of larval O. lienalis was noted early in the culture period, but neither species continued development to the fifth stage.     

Short communication: concomitant malaria and filariasis infections in Georgetown,Guyana

Lymphatic filariasis and malaria are endemic in Guyana, South America. To determine the prevalence of concomitant infections, we conducted a 1-year survey of febrile patients attending the malaria (day) and filariasis (night) clinics in Georgetown. In all, 1278 thick blood smears were collected: 769 for filariasis, of which 103 were positive for Wuchereria bancrofti, and three for both W. bancrofti and malaria parasites; and 509 for malaria, 21 of which tested positive for malaria and 17 for both malaria and filariasis. The age groups and sex of the infected persons with malaria and W. bancrofti are described. These results suggest that the incidence of concomitant infections in Guyana may be quite low but efforts should be made to reduce the disease burden in Georgetown, Guyana.     

Colonic volvulus. Etiology and management

Colonic volvulus accounts for 1-7% of cases of large bowel obstruction in the United States and Western Europe. It is, however, a much commoner condition in parts of Africa, South Asia and South America. Volvulus is thought to be an idiopathic condition, probably with an anatomical basis, particularly in cecal volvulus. Some cases are, however, secondary to a known condition such as Chagas' disease. The sigmoid colon is involved in 65-80% of cases and the right colon in 15-30%. Transverse colon and splenic flexure volvulus are rare. Emergency surgery has in the past been associated with a high mortality. Nonoperative, tube decompression of sigmoid volvulus has been the single most important advance in the management of the condition--this has allowed surgery to be deferred to an elective schedule and performed on a fitter patient with a prepared bowel. Emergency surgery is still required for a minority of patients--those in whom tube decompression is unsuccessful; in those with signs of gangrenous bowel and patients with volvulus proximal to the sigmoid. When the bowel is not viable, resection is mandatory. In patients with a viable colon, there are several options. Sigmoid resection and colostomy for sigmoid volvulus and detorsion, cecopexy and tube cecostomy as a combined procedure for cecal volvulus are the usually recommended procedures.     

Comparison of thick blood smear and saponin haemolysis for the detection of Loa loa and Mansonella perstans infections

In an endemic area, Loa loa and Mansonella perstans microfilariae were detected by the examination of 5 ml blood in respectively 7.4 and 26.2% of subjects who would have been erroneously considered amicrofilaraemic by the conventional method of two thick blood smears (40 microliters blood). Correction factors to be applied to the results obtained with thick blood films in order to approach the true parasitological prevalences were 1.5 for L. loa and 1.6 for M. perstans. In addition, the analysis of a large volume of blood provides a better estimation of microfilarial load of the parasitized population.