Triatoma brasiliensis is considered as one of the most important Chagas disease vectors in the northeastern Brazil. This species presents chromatic variations which led to descriptions of subspecies, synonymized by Lent and Wygodzinsky (1979)

Triatoma brasiliensis is one of the most important vectors of Chagas disease in the semiarid Lent, 1941 and T. brasiliensis macromelasoma Galvão, 1956. These subspecies differ mainly in their cuticle colour pattern and were regarded as synonyms by Lent and Wygodzinsky (1979) Galvão, 1956. Their descriptions are based on the different chromatic patterns of pronotum, hemelytron and legs. A taxonomic key for the different subspecies can be found in Galvão (1956). These subspecies were synonymized by Lent and Wygodzinsky (1979), who simply asserted that "inter-grading forms are frequent". Whether T. brasiliensis consists of different melanic populations or the chromatic patterns observed are due to interspecific variation is unknown.In order to study this question, isoenzymatic, morphological and behavioural studies have been undertaken: morphological characters of the geni- tal structures show considerable individual heterogeneity, thus making the differentiation of the chromatic patterns with these structures impossible. However, observations on the homogeneity and stability of colour patterns of colonies reared in laboratory and the allopatry registered during field captures, indicate that T. brasiliensis presents distinct geographic populations (Costa et al. 1996c). Studies on the biology, feeding sources and natural infection of the different chromatic variants have been carried out (Costa et al. 1995a, b). The results using multilocus enzyme electrophoresis for comparing these distinct populations of T. brasiliensis are reported here. MATERIALS AND METHODSThe insects -One hundred and twenty specimens belonging to four chromatic populations of T. brasiliensis were tested: 30 F1 adults (15 females and 15 males) of each different chromatic patterns were used from colonies initiated with individuals collected from the field. The specimens captured were found in isolated colonies in different ecotopes. The localities where T. brasiliensis specimens were collected, the populations they represent and number of founder individuals are given in Table I. Voucher specimens are deposited in the Entomological Collection of Instituto Oswaldo Cruz-FIOCRUZ, Rio de Janeiro.

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Abstract. To determine the influence of onchocercal eye disease on the intraocular pressure of the Yanomami Tribe Aratha-ú of Roraima State, Brazil, considered endemic for onchocerciasis, a total of 86 patients were submitted to an ophthalmologic exam that included external examination, slit lamp examination, intraocular pressure measurement, and a fundus ophthalmoscope examination. A high prevalence of onchocerciasis-related eye lesions was encountered in 68.6% of the patients. Punctate keratitis and microfilariae in the anterior chamber were found in~28%. The mean of intraocular eye pressure found was 10.47 mm of Hg.

According to the World Health Organization (WHO 2000) more than 120 million people, worldwide, live under risk of acquiring onchocerciasis and 18 million are infected. One third of those infected manifest dermatitis and 500,000 present serious visual problems with approximately 1% developing blindness. Indeed, 270,000 individuals are blind from this etiology worldwide. This disease is caused by infection with Onchocerca volvulus (Nematoda: Onchocercidae) and is endemic to Africa, the Arabian Peninsula, and Latin America, where it occurs in parts of Brazil, Colombia, Ecuador, Guatemala, Mexico, and Venezuela. In Brazil, the only known active focus of the disease is located in the Amazonian region, and extends across the border to form the southern focus of Venezuela. It corresponds to more or less the whole territory of the Yanomami in the northwest of the state of Roraima and central north of the state of Amazonas (Shelley 1991(Shelley , 2002, exposing 13,767 indians to the infection (Funasa 2002).In the New World the control program has been sponsored by the Onchocerciasis Elimination Program for the Americas (OEPA). This program has as its main strategy the elimination of the disease through the semi-annually distribution of the ivermectin (Mectizan™) for 10 to 15 years to the population at risk (Blanks et al. 1998). This approach has been demonstrated to result in a decrease of microfilariae rates in the skin which gives immediate clinical benefit and reduces the possibility of infecting new vectors which is expected to reduce or eliminate transmission (Greene et al. 1989, Duke 1990.In simuliids, the classic parasitological method for the parasite detection (by dissection and examination of vectors) is unsuitable for high throughput analysis because it is time consuming and requires high levels of training, for example it requires the accurate morphological identification of the larvae.Since the 1990s, the polymerase chain reaction (PCR) amplification of an Onchocerca-specific repeated DNA sequence (O-150) has been used to detect and identify O. volvulus (Meredith et al. 1991, 1994, Zimmerman et al. 1992, Fischer et al. 1996, Merriweather & Unnasch 1996, Unnasch & Meredith 1996. However, in populations of vectors with a low prevalence of infection (as would be expected during an onchocerciasis control program using ivermectin, for example) large numbers of flies would have to be processed to obtain an accurate estimate of infection, which would be timeconsuming and expensive. However, the O-150 PCR has proved to have a high analytical sensitivity, being able to detect a single infected fly in pools containing up to 100 flies (Katholi et al. 1995). Therefore, a statistical model has been developed by Katholi et al. (1995) to determine the prevalence of infection in the simuliid population, based on the prevalence of infection in pools of vectors, and it has been demonstrated that this method reveals a prevalence of infected flies statistically similar to the rates obtained by traditional entomological dissect...