The occurence of black spot disease in Astyanax aff. fasciatus (characiformes: characidae) in the Guaíba Lake basin, RS, Brazil / Ocorrência da doença dos pontos pretos em Astyanax aff. fasciatus (characiformes: characidae) na bacia do lago Guaíba, RS, Brazil

Black spot disease is common in freshwater fish and is usually caused by the metacercaria stage of digenetic trematodes, normally from the Diplostomidae family. The present study evaluated the prevalence and intensity of this disease in Astyanax aff. fasciatus (Teleostei: Characiformes) in the Guaíba Lake basin (RS, Brazil), including body parts assessment and the points of sampling with higher occurrence of black spots. Fish samples were taken seasonally from December 2002 until October 2004. The samples were collected with the use of a seine net at eleven points. The specimens were fixed in 10% formalin and stored in 70% ethanol. Black spot disease showed a low frequency in the Guaíba lake basin (2.07%) and no specificity to the species Astyanax aff. fasciatus was observed. A high prevalence among the individuals and high intensity of infection levels was found in the ventral and dorsal regions in relation to other body parts (e.g., pectoral, pelvic and anal regions). Among the sampling points studied, we observed a higher prevalence on samples collected at points Gasômetro, Saco da Alemoa and Sinos, located in open areas with less occurrence of mollusks.

A doença dos pontos pretos é comum em peixes de água doce, sendo provocada por metacercárias de trematódeos digenéticos, normalmente da família Diplostomidae. Este estudo avaliou a prevalência desta doença em Astyanax aff. fasciatus (Teleostei: Characiformes) da bacia hidrográfica do lago Guaíba (RS) e avaliou as regiões do corpo e pontos de amostragem de maior ocorrência. As amostragens foram realizadas sazonalmente de dezembro de 2002 até outubro de 2004 e os exemplares coletados com redes de arrasto do tipo picaré em onze pontos da bacia estudada. Os peixes foram fixados em formaldeído a 10% e conservados em etanol 70%. A doença dos pontos pretos demonstrou baixa freqüência para as amostras coletadas na bacia hidrográfica do lago Guaíba (2,07%) e não foi verificada especificidade com a espécie A. fasciatus. Maior prevalência e intensidade de infecção ocorreram nas regiões ventral e dorsal em relação às outras partes do corpo (ex: regiões peitoral, pélvica e anal). Entre os pontos estudados, foi observado elevada prevalência nas amostras coletadas nos pontos Gasômetro, Saco da Alemoa e Sinos, localizados em áreas mais abertas e com menor ocorrência de moluscos.

The occurence of black spot disease in Astyanax aff. fasciatus (Characiformes: Characidae) in the Guaíba Lake basin, RS, Brazil.

Black spot disease is common in freshwater fish and is usually caused by the metacercaria stage of digenetic trematodes, normally from the Diplostomidae family. The present study evaluated the prevalence and intensity of this disease in Astyanax aff. fasciatus (Teleostei: Characiformes) in the Guaíba Lake basin (RS, Brazil), including body parts assessment and the points of sampling with higher occurrence of black spots. Fish samples were taken seasonally from December 2002 until October 2004. The samples were collected with the use of a seine net at eleven points. The specimens were fixed in 10% formalin and stored in 70% ethanol. Black spot disease showed a low frequency in the Guaíba lake basin (2.07%) and no specificity to the species Astyanax aff. fasciatus was observed. A high prevalence among the individuals and high intensity of infection levels was found in the ventral and dorsal regions in relation to other body parts (e.g., pectoral, pelvic and anal regions). Among the sampling points studied, we observed a higher prevalence on samples collected at points Gasômetro, Saco da Alemoa and Sinos, located in open areas with less occurrence of mollusks.

[The etiology and diagnosis of "black spot disease" of fish]. / Ob étiologii i diagnostike "chernopiatnistogo zabolevaniia" ryb.

Some traditional points of view on the black spot disease in fishes caused by the metacercariae of the trematode Posthodiplostomum cuticola are revised. The black spot disease should be considered as one of several symptoms appeared in freshwater and sea fishes in cases of infection with certain parasite species. Up to present days, more than 30 parasite species causing similar symptoms are recognized. And among them 8 such species have been recorded in fishes of the Volga-Caspian region.

A clinical classification and grading system of the cutaneous changes in onchocerciasis.

Although onchocerciasis is one of the most important diseases of the skin and eye in the tropical world, to date there has been no formal consensus regarding the description and terminology of skin lesions. Furthermore, the contribution of cutaneous pathology to the morbidity and socio-economic effects of the disease has been largely neglected. We present a clinical classification and grading system for recording the cutaneous changes of onchocerciasis, and propose that this system be used as a standard method of description to convey clinical information between workers in all endemic areas to assist local and comparative research.

Prevalence of depigmentation of the shins: a simple and cheap way to screen for severe endemic onchocerciasis in Africa.

The prevalence of skin depigmentation in the pretibial region is closely correlated in the adult Congolese population with conventional indices (microfilarial index, mean microfilarial density, cyst index) for the evaluation of endemic onchocerciasis. Individuals over 15 years of age in endemic villages who had a microfilarial index of 80-90%, had a cystic index of 60-70% and a pretibial depigmentation index about 20% (30-40% for individuals aged > 50 years). Thus, in Africa, this new evaluation index offers a simple, noninvasive, quick and cheap way to identify areas where the level of endemic onchocerciasis is probably high and which are likely to benefit from an anti-onchocerciasis campaign.

PIP: Skin depigmentation is a classic diagnostic sign of onchocerciasis and presents typically as an irregular, flat spot surrounded by slightly hyperpigmented zones. The depigmentation occurs mainly on the shins. The prevalence of skin depigmentation has been proposed as a marker for evaluating the endemicity of onchocerciasis in Nigeria, but has been contested for use in South America on the grounds of non-specificity. The microfilarial index currently used to assess the level of onchocerciasis endemicity is relatively time-consuming, costly, and harbors the risk of transmitting viral infections during mass screenings. 991 people over 15 years of age of mean age 55.4 years in five villages in the Congo endemic for onchocerciasis participated in this study. Individuals who had a microfilarial index of 80-90% had a cystic index of 60-70% and a pretibial depigmentation index of approximately 20%. The authors conclude that the existence of shin depigmentation as an evaluation index in Africa offers a simple, noninvasive, quick, and inexpensive way to identify areas where the level of endemic onchocerciasis is probably high and which are likely to benefit from an anti-onchocerciasis campaign. Although the new index does not allow total specificity, the incidence of shin depigmentation among patients with African onchocerciasis is such that there is probably little risk of confusing holo- or hyperendemic zones with an area where leprosy or treponema are endemic. In the absence of onchocerciasis, bites from Simulium spp. flies may also be responsible for skin depigmentation, as may be streptocerciasis. In this latter condition, however, the predominant site of depigmentation is not the shin. The authors have observed no notable prevalence of shin depigmentation in northern Congo, which is infested with S. albivirgulatum flies, but with no onchocerciasis transmission, and where there are also zones of streptocerciasis.

Upper extremity swelling and hyperpigmentation due to onchocerciasis in an American.

An American woman who had lived in Equatorial Guinea was seen in the United States with intermittent swelling, pruritus, hyperpigmentation, and mild cutaneous atrophy of the right arm. Filarial diseases were considered in the differential diagnosis; skin snips subsequently revealed Onchocerca volvulus microfilariae. There was no evidence of ocular involvement. The case illustrates the importance of obtaining a history of international travel, the need to consider "exotic" parasitic diseases in travelers returning from the tropics, and several of the presenting features of onchocerciasis. In the past, onchocerciasis was treated with diethylcarbamazine and suramin, both of which have appreciable toxicity. A major recent advance has been the introduction of ivermectin, which appears to be more effective and less toxic, and is currently undergoing clinical evaluation in the United States and abroad.

Parasitologic survey of onchocerciasis (river blindness) in Babana District, Kwara State, Nigeria.

This study, made between November 1982 and January 1983 to ascertain the prevalence of onchocerciasis in the Babana District of Borgu Local Government Area, Kwara State, Nigeria, showed that 483 (48.6%) of the 993 subjects skin-snipped in 12 communities were infected. The infection rate was significantly higher (P less than 0.001) for males (57.7%) than for females (37.0%), for subjects above 10 years of age (54.0%) than for those who were younger (10.7%), and for the Fulanis (63.8%) than for the Bokos (48.3%). Although various indications suggest that this district has a history of long-standing onchocerciasis, the knowledge of river blindness and its association with blackflies was poor throughout the district and, except for two teachers, no other subjects had ever received onchocercal chemotherapy. These factors, apparently, account for the frequent occurrence and severity of various clinical manifestations and complications of onchocerciasis identified in the district.