Early human infection with Onchocerca volvulus is associated with an enhanced parasite-specific cellular immune response.

The immune response after early exposure to or infection with Onchocerca volvulus was investigated in an autochthonous focus caused by the migration of infected persons to a previously unaffected area in Ecuador. Peripheral blood mononuclear cell (PBMC) proliferative and cytokine responses (interferon [IFN]-gamma and interleukin [IL]-5) to filarial antigens were measured in 14 subjects with serologic evidence of exposure and in 7 subjects with evidence of dermal microfilarial DNA and were compared with responses in 43 subjects with chronic O. volvulus infections. PBMC proliferative and cytokine responses (IFN-gamma and IL-5) to parasite antigens were elevated in the early exposure/infection group, compared with those in the chronic infection group. Addition of an IL-10-neutralizing antibody to filaria antigen-stimulated cultures resulted in significantly elevated proliferative responses in the chronic infection group. The findings suggest that early exposure and early parasite patency are associated with a vigorous cellular response, but, as infections become chronic, the cellular response becomes down-regulated, partly through an IL-10-dependent mechanism.

A new flux-orientated concept to derive critical levels for ozone to protect vegetation.

The current European critical levels for ozone (O3) to protect crops, natural and semi-natural vegetation and forest trees are based on a relative small number of open-top chamber experiments with a very limited number of plant species. Therefore, the working group "Effects of Ozone on Plants" of the Commission on Air Pollution Prevention of the Association of German Engineers and the German Institute of Standardization reanalysed the literature on O3 effects on European plant species published between 1989 and 1999. An exposure-response relationship for wild plant species and agricultural crops could be derived from 30 experiments with more than 30 species and 90 data points; the relationship for conifer and deciduous trees is based on 20 experiments with nine species and 50 data points. From these relationships maximum O3 concentrations for different risk stages are deduced, below which the vegetation type is protected on the basis of the respective criteria. Because it is assumed that the fumigation concentrations reflect the O3 concentrations at the top of the canopy, i.e. the upper surface boundary of the quasi-laminar layer if the micrometeorological big-leaf approach is applied, the application of these maximum O3 concentrations requires the transformation of O3 concentrations measured at a reference height above the canopy to the effective phytotoxic concentrations at the top of the canopy. Thus, the approach described in this paper is a synthesis of the classical concept of toxicology of air pollutants (critical concentrations) and the more toxicological relevant dose concept.

Albendazole treatment of children with ascariasis enhances the vibriocidal antibody response to the live attenuated oral cholera vaccine CVD 103-HgR.

Because concurrent infections with geohelminth parasites might impair the immune response to oral vaccines, we studied the vibriocidal antibody response to the oral cholera vaccine CVD 103-HgR in children infected with Ascaris lumbricoides and investigated the effect of albendazole pretreatment on the postvaccination response. Children with ascariasis were randomized to receive either 2 sequential doses of 400 mg of albendazole or placebo. After the second dose, CVD 103-HgR was given, and serum vibriocidal antibody levels were measured before and 10 days after vaccination. Postvaccination rates of seroconversion were greater in the treatment group that received albendazole (P=.06). Significantly greater rates of seroconversion and geometric mean titer were observed in the albendazole group in subjects with non-O ABO blood groups. A significant association was observed between vibriocidal seroconversion rates and treatment group, suggesting that A. lumbricoides infections impair the immune response to oral cholera vaccine, particularly in subjects of non-O blood groups.

Eotaxin and RANTES expression by the dermal endothelium is associated with eosinophil infiltration after ivermectin treatment of onchocerciasis.

The roles of eotaxin, RANTES, and MCP-3 expression in eosinophil recruitment to the site of parasite killing that occurs following ivermectin treatment of onchocerciasis were assessed in the skin of 13 Onchocerca volvulus-infected subjects and two noninfected controls before and after ivermectin treatment. Adverse reactions in infected subjects were associated with the appearance of eosinophils in the dermis as part of a perivascular inflammatory infiltrate. Although no expression of RANTES and eotaxin was seen in dermal vascular endothelial cells in biopsies taken before treatment (nor at any time in the skin of uninfected controls), endothelial expression of both eotaxin and RANTES was noted by 24 h following treatment. While RANTES expression was transient, eotaxin expression increased in parallel with increasing eosinophil recruitment up to 60 h posttreatment. These observations indicate that endothelial expression of eotaxin and RANTES may have an important role in eosinophil recruitment into the skin during helminth-killing reactions.

Genetic analysis of leishmania parasites in Ecuador: are Leishmania (Viannia) panamensis and Leishmania (V.) Guyanensis distinct taxa?

In the course of an epidemiologic survey in Ecuador, the following collection of Leishmania stocks was isolated: 28 from patients with clinical signs of leishmaniasis, 2 from sloths, 1 from a dog, and 4 from sand flies. For genetic characterization of these stocks, multilocus enzyme electrophoresis (MLEE) and random amplified polymorphic DNA (RAPD) were used. Twenty six of the 35 stocks were identified as either Leishmania (V.) panamensis or L. (V.) guyanensis, 2 stocks were identified as L. (V.) braziliensis, the 2 stocks from sloths showed specific genotypes, and 5 stocks were characterized as hybrids between L. (V.) braziliensis and L. (V.) guyanensis. These data show that genetic diversity of Leishmania in Ecuador is high and that L. (V.) panamensis/guyanensis is the dominant group in this country. The genetic analysis questioned the distinctness between the two species L.(V.) panamensis and L. (V.) guyanensis, since MLEE and RAPD data did not indicate that L. (V.) panamensis and L. (V.) guyanensis correspond to distinct monophyletic lines. Population genetic analysis performed on the L. (V.) panamensis/guyanensis group favors the hypothesis of a basically clonal population structure.

Human onchocerciasis and tetanus vaccination: impact on the postvaccination antitetanus antibody response.

To investigate whether helminth infections may affect the efficacy of vaccines by impairing the immune response to nonparasite vaccine antigens, we compared the antibody responses to tetanus toxoid (TT) after tetanus vaccination in 193 subjects with Onchocerca volvulus infection with 85 comparable noninfected controls. After vaccination, the proportions of subjects in each group attaining protective levels of antitetanus antibodies were similar (96.9% infected versus 97.6% noninfected). Postvaccination increases in antitetanus immunoglobulin G (IgG) and the predominant IgG isotype, IgG1, were equivalent in both groups, as were increases in specific IgG4 and IgE; however, significantly greater increases in specific IgG2 (P < 0.05) and IgG3 (P < 0.001) were observed in the noninfected group. Stratification of the O. volvulus-infected group into two groups representing light and heavy infections revealed a significantly impaired antitetanus IgG response in those with heavy infections compared to those with light infections (P < 0.01) or no infection (P < 0.05). The impact of concurrent intestinal helminth infections on the antitetanus response was also examined; an increased IgG4/IgE ratio was seen in those infected with Strongyloides stercoralis (P < 0.05) and when all helminth infections were combined as a single group (P < 0.05). These findings indicate that concurrent infection with O. volvulus does not prevent the development of a protective antitetanus response, although heavier O. volvulus infections are able to alter the magnitude of this response, and concurrent helminth infections (O. volvulus and intestinal helminths) may alter TT-specific antibody isotype responses.

Treatment of human pulmonary paragonimiasis with triclabendazole: clinical tolerance and drug efficacy.

An open clinical trial to determine the efficacy and tolerability of postprandial doses of triclabendazole against Paragonimus mexicanus in 62 patients with pulmonary paragonimiasis from the Ecuadorian Amazon region was performed. Praziquantel was used as therapeutic control. Patients were allocated at random to the following 4 therapeutic regimens: triclabendazole, 5 mg/kg once daily for 3 d (16 patients), 10 mg/kg twice on one day (15 patients), and 10 mg/kg in a single dose (16 patients), and praziquantel, 25 mg/kg thrice daily for 3 d (15 patients). Clinical tolerance, based on the frequency and severity of adverse reactions, was superior in all 3 triclabendazole regimens to that of praziquantel. No alteration was observed in hepato-renal functions or haematological values. The clinical symptoms resolved at a comparable rate in all 4 treatment groups. A more rapid parasitological response to treatment, as determined by the reduction in the average number of parasite eggs found in sputum, was seen in patients treated with triclabendazole than with praziquantel. By day 90, 60 patients had no egg detected in their sputum; 2 patients, treated with a single dose of 10 mg/kg, had a few and were re-treated with triclabendazole (5 mg daily for 3 d). On day 365, none of the patients had eggs in their sputum. Triclabendazole can be recommended as an alternative drug of choice for the treatment of pulmonary paragonimiasis; it is as effective as praziquantel in clearing infections and better tolerated.

Impaired tetanus-specific cellular and humoral responses following tetanus vaccination in human onchocerciasis: a possible role for interleukin-10.

Onchocerca volvulus infection has been associated with impaired cellular responses to parasite antigens, an impairment that may also extend to nonparasite antigens. To investigate the mechanism of this impaired immune response, the effect of concurrent O. volvulus infection on the immune response to tetanus toxoid (TT) following tetanus vaccination was studied. The proliferative, cytokine, and antibody response to TT of O. volvulus-infected subjects (n = 19) and comparable noninfected controls (n = 20) were studied before and 6 months after vaccination with TT. Following vaccination, antibody levels, proliferative responses, and levels of interferon-gamma were significantly greater in noninfected subjects (P < .05, .001, and .05, respectively); however, infected subjects produced interleukin-10, but noninfected controls did not (P < .001). These studies indicate that concurrent infection with O. volvulus can diminish the immune response to an unrelated antigen (TT) by a mechanism that is likely to involve interleukin-10.

Current status of onchocerciasis in Colombia.

To assess the current epidemiologic status of onchocerciasis in Colombia two surveys were undertaken in 1995 in a suspected new focus on the border between Colombia and Ecuador and in the known focus located on the Micay River. No new focus was found along the Colombia-Ecuador border. In the known focus, communities along the upper Micay River and its tributaries were surveyed; 655 adults underwent physical examinations and skin biopsies. Infected individuals were found almost exclusively in the community of Naiciona, where prevalence of infection was 40% (36 of 91). Polymerase chain reaction detection of onchocercal DNA in skin snips correlated with the skin-snip biopsy results. The prevalence of punctate keratitis, the only ocular manifestation found, was 33%. A rapid entomologic assessment demonstrated Simulium exiguum infected with Onchocerca volvulus. This is the first finding in Colombia of naturally infected black flies and confirms S. exiguum as a vector species. These data will be used for implementing a control program using periodic ivermectin distribution.

Macrofilaricidal effects of chloroquine on adult Onchocerca volvulus by local infiltration of palpable onchocercal nodules

O efeito macrofilaricida da infiltração local, com uma alta concentração de cloroquina, dentro da cápsula do nódulo oncocercótico sobre o verme adulto de Onchocerca volvulus foi determinado. Seis semanas depois da infiltração, estudos histopatológicos de nódulos simple demonstraram todos os vermes adultos mortos. Em conglomerados de nódulos a ação da cloroquina foi só sobre os vermes adultos do nódulo infiltrado, não acontecendo a difusão da droga aos nódulos adjacentes. A infiltração de cloroquina a nódulos novos ou de recente formação reduz a carga de vermes adultos dos indivíduos parasitados e pode ser uma alternativa para os altos custos das nodulectomias.

The macrofilaricidal effects of local infiltration of high concentrations of chloroquine into the capsule of onchocercal nodules on adult worms of Onchocerca volvulus was determined. Six weeks post infiltration, histological examination of single nodules showed all adult worms to be dead. With nodule conglomerates, there was localized action of chloroquine only on the adult worms in the infiltrated nodule, with no diffusion of the drug to adjacent nodules. Chloroquine infiltration of young, recently formed nodules to reduce the adult worm load of infected individuals may be an alternative method to costly nodulectomy.

Successful control of onchocerciasis with community-based ivermectin distribution in the Rio Santiago focus in Ecuador.

Onchocerciasis is a major blinding disease in equatorial Africa and Central and South America. Ivermectin is a safe and effective drug in the treatment of this disease and now forms the basis of disease control in most endemic areas. We report the findings of long-term control of this infection in the Río Santiago focus in Ecuador, between January 1990 and December 1996, using a strategy of giving ivermectin treatments biannually in hyperendemic communities and annually in meso- and hypoendemic communities. Ivermectin was administered by local health workers from each community. A high level of compliance to ivermectin was achieved, with 81.9% to 98.0% of those eligible receiving the drug at each treatment instance. The impact of ivermectin therapy was monitored using a cohort of 120 randomly selected infected individuals from 8 hyperendemic communities. The geometric mean microfilarial density of this group declined from 19.3 to 0 mf/mg over the 84-month observation period. Ivermectin had a significant impact on anterior segment ocular disease, acute onchodermatitis and sowda. The rate of infection of blackflies declined from 1.1% in 1989-0.08% in 1996, which is below the vectorial capacity of the Simulium vector and, as no new nodules were detected after 1994 and no children under 5 became infected over the observation period, it is likely that the transmission of this infection was interrupted in the study area.

Severe digestive pathology associated with chronic Chagas' disease in Ecuador: report of two cases.

DNA extracted from peripheral blood of two Ecuadorian patients showing severe digestive pathology was amplified by the polymerase chain reaction using a Trypanosoma cruzi specific oligonucleotide primers derived from the primary sequence of a cDNA encoding for a 24 kDa excretory/secretory protein. The positive PCR results together with the clinical findings confirmed that both patients had a digestive pathology due to Chagas' disease. This pathology could be more frequent than previously described in the chagasic endemic regions of Andean countries.

Severe digestive pathology associated with chronic Chagas' disease in Ecuador: report of two cases

DNA extracted from peripheral blood of two Ecuadorian patients showing severe digestive pathology was amplified by the polymerase chain reaction using a Trypanosoma cruzi specific oligonucleotide primers derived from the primary sequence of a cDNA encoding for a 24 kDa excretory/secretory protein. The positive PCR results together with the clinical findings confirmed that both patients had a digestive pathology due to Chagas' disease. This pathology could be more frequent than previously described in the chagasic endemic regions of Andean countries.

DNA obtido do sangue periférico de dois pacientes equatorianos, que apresentavam severa patologia digestiva, foi amplificado pela "polymerase chain reaction" (PCR) utilizando os oligonucleotídoes específicos do Trypanosoma cruzi, derivados de uma seqüência primária de cDNA codificado de 24 kDa proteína excretória/secretória. Os resultados positivos da PCR junto com os achados clínicos confirmam que os dois pacientes tinham uma patologia digestiva de origem chagásica. Esta patologia poderia ser mais freqüente que a descrita previamente nas regiões endêmicas chagásicas das cidades dos Andes.

Evidence for hybridization by multilocus enzyme electrophoresis and random amplified polymorphic DNA between Leishmania braziliensis and Leishmania panamensis/guyanensis in Ecuador.

The taxonomic attribution of four Leishmania stocks isolated from humans in Ecuador has been explored by both multilocus enzyme electrophoresis and random amplified polymorphic DNA. For three loci, MLEE results showed patterns suggesting a heterozygous state for a diploid organism, while the corresponding homozygous states are characteristic of the Leishmania panamensis/guyanensis complex and Leishmania braziliensis, respectively. Other enzyme loci showed characters attributable to either the L. panamensis/ guyanensis complex or L. braziliensis. RAPD profiles exhibited for several primers a combination of the Leishmania panamensis/ guyanensis complex and L. braziliensis characters. These data hence suggest that the four stocks are the result of hybridization between L. panamensis/guyanensis and L. braziliensis. MLEE data show that the results cannot be attributed to either mixture of stocks, or an F1 in the framework of a simple Mendelian inheritance.

Onchocerciasis and reproductive health in Ecuador.

A retrospective study was performed comparing the number of spontaneous abortions in a hyperendemic area for onchocerciasis in Ecuador before and after invermectin treatment with that of a comparable non-endemic area. The frequency of spontaneous abortions was associated with a change in the community microfilarial load, suggesting that there may be a relationship between spontaneous abortions and infection with Onchocerca volvulus. In the endemic area, a significantly greater rate of spontaneous abortions was seen in the period before ivermectin distribution compared to that after the start of ivermectin treatments every 6 months. In the non-endemic area, no change in the rate of spontaneous abortions was seen over the same time period. In addition to the well-documented improvements in skin and ocular disease, ivermectin may also improve the reproductive health of endemic populations.

Human infection with Onchocerca volvulus does not affect the T helper cell phenotype of the cellular immune response to mycobacterial antigen.

In order to determine whether infection with Onchocerca volvulus might modify the immune response to mycobacterial antigen, the proliferative and cytokine responses of peripheral blood mononuclear cells from 117 persons infected with O. volvulus and 36 non-endemic control subjects were compared. Tuberculin-stimulated cellular proliferative responses and production of Th1-type cytokines (interferon gamma) were reduced in persons infected with O. volvulus compared to controls. However, there was no evidence of polarization of the immune response towards a Th2-type phenotype (interleukin 5) in infected individuals compared to controls.