Individual cases of autochthonous malaria in Evros Province, northern Greece: entomological aspects.

Prompted by four autochthonous cases of malaria in 1994 and 1995 in Evros Province, northern Greece, we conducted an entomological study between 1997 and 1999 in Nipsa and Chandras, rural locations where two of the four cases had occurred, and in Feres where two additional autochthonous malaria cases had been diagnosed in 1998. In Nipsa and Chandras, we identified 29 Anopheles breeding sites and characterized them by physicochemical parameters. Larvae were collected both at these sites and in a brackish water breeding site near Feres in the Evros River delta. Adults were caught in sheds at all three locations. Morphology was used to classify larvae and adults as A. superpictusor as species belonging to the A. claviger or A. maculipennis species complexes. The latter were further identified by PCR as being A. maculipennis s.s., A. melanoon and A. sacharovi. Of the A. maculipennis complex larvae collected inland, approximately 94% were A. maculipennis s.s. and 6% A. melanoon, whereas all larvae collected in the coastal region were A. sacharovi. In contrast, the A. maculipennis adults were A. maculipennis s.s. and A. melanoon (both 47%), and A. sacharovi (6%). In the coastal region, no A. maculipennis s.s. adults were caught. The ratio of A. melanoon adults collected to A. sacharovi was about 3:1. As shown by a bloodmeal ELISA, only 5 of 266 fed females (1.9%) had ingested human blood, whereas 232 (87%) had fed on goats. Of the mosquitoes containing human blood, two were A. melanoon, one A. sacharovi and one A. maculipennis s.s. One human blood specimen could no longer be assigned to a particular mosquito.

Individual cases of autochthonous malaria in Evros Province, northern Greece: serological aspects.

From 1994 to 1995 four presumably autochthonous malaria cases were diagnosed by blood smear microscopy in Evros Province, northern Greece. Alarmed by these unexpected infections a serological survey was performed from 1997 to 1999 in ten rural villages, including those where the malaria cases had occurred. Among the 1,102 blood samples examined, nine turned out to contain specific antibodies against plasmodial parasites as detected by indirect fluorescent antibody test, including two of the former patients. The remaining seven samples were taken from healthy individuals with no history of recent infection or of having travelled to endemic areas. A further 21 sera showed borderline reactivity with Plasmodium falciparum antigen. Although no retrospective examination of the blood specimens could be performed to confirm the serological results by direct parasite detection, we can conclude that at least the seropositive persons have actually undergone infection with malaria parasites but developed no or only mild clinical symptoms which went unnoticed. It is becoming obvious that even in European countries where climatic and vector conditions are favourable for the development of the parasite there is a potential risk of incidental malaria transmission by indigenous Anopheles mosquitoes.