Entomologic and avian investigations of an epidemic of West Nile fever in Romania in 1996, with serologic and molecular characterization of a virus isolate from mosquitoes.

Abstract

Abstract. Between July and October 1996, a West Nile (WN) fever epidemic occurred in the southern plain and Danube Valley of Romania and in the capital city of Bucharest, resulting in hundreds of neurologic cases and 17 fatalities. In early October 1996, entomologic and avian investigations of the epidemic were conducted in the city of Bucharest and nearby rural areas. Thirty (41%) of 73 domestic fowl sampled had neutralizing antibody to WN virus, including 5 of 13 ducks (38%), 1 of 1 goose, 19 of 52 chickens (37%), 1 of 1 peahen, and 4 of 6 turkeys (67%). Seroprevalence in domestic fowl (27%, or 7 of 26) from the urban Bucharest site was not significantly different (P ϭ 0.08, by Fisher's exact test) than rates at three rural sites (50%, or 23 of 46). Serum collected from one of 12 Passeriformes, an Erithacus rubecula, was positive for neutralizing antibody to WN virus. A total of 5,577 mosquitoes representing seven taxa were collected. Culex pipiens pipiens accounted for 96% of the mosquitoes collected. A single virus isolate, RO97-50, was obtained from a pool of 30 Cx. p. pipiens females aspirated from the walls and ceiling of a blockhouse located near the center of Bucharest, resulting in a minimum infection rate of 0.19 per 1,000. Antisera prepared against RO97-50 failed to distinguish among RO97-50, WN virus strain Eg101, and Kunjin (KUN) virus strain MRM16. A 2,323-basepair DNA fragment of the envelope (E) glycoprotein gene from RO97-50 and a Romanian WN virus strain obtained from a human cerebrospinal fluid sample, RO96-1030, were sequenced. Phylogenetic analyses of 23 WN virus strains and one KUN virus strain using the amino acid and nucleotide sequences for a small portion of the E gene suggest the existence of two large lineages of viruses. Bootstrap analysis of the nucleotide alignment indicated strong support (95%) for a lineage composed of WN virus strains from northern Africa, including isolates from Egypt and Algeria, and west, central, and east Africa, all of the European isolates, those from France and Romania, an Israeli isolate, and an isolate of KUN virus from Australia. The nucleotide sequence of RO97-50 was identical to the sequence of a WN virus isolate obtained from Cx. neavei mosquitoes from Senegal and Cx.

The Japanese Encephalitis Serological Group of Flaviviruses: a Brief Introduction to the Group

“…Berthet and colleagues (BERTHET et al 1997) clearly demonstrated that there were two distinct genetic lineages of WN viruses. This was confirmed and extended in other studies (JIA et al 1999;LANCIOTTI et al 1999;SAVAGE et al 1999;SCHERRET et al 2001). One lineage, lineage I, comprises four major clades including most isolates from Africa, Europe and India, as well as the New York isolates and the Australian Kunjin viruses; the second lineage comprises the original prototype strain, and isolates from West, Central and East Africa, and from Madagascar.…”

West Nile virus infection of horses

“…The identification and classification of WNV isolates has been made using these reagents in virus neutralisation and indirect immunofluorescence tests, but the analysis of nucleotide sequences encoding the protein E is perhaps what has revealed more clearly the relationship between various WNV isolates. Thus, it has been found that WNV viruses fall into two distinct lineages [11,78,80]. Lineage 1 includes viruses isolated outside and inside the African continent which have been associated with recent epidemics of increased severity in humans and horses, whereas lineage 2 comprises viruses that have only been found to circulate in enzootic cycles in birds in Africa.…”

La fièvre du Nil occidental et la fièvre catarrhale ovine, deux viroses en progression inattendue

“…La fièvre du Nil occidental est une arbovirose dont plusieurs épi-démies/épizooties ont été observées en Europe, sur le pourtour du bassin méditerranéen et en Amérique du Nord, ces dix dernières années (Hannoun et al 1964 ;Savage et al 1999). Le VWN a été isolé dans une soixantaine d'espèces de moustiques aux États-Unis d'Amérique (Higgs et al 2004) et dans au moins 75 espèces appartenant à 10 genres d'insectes différents dans le reste du monde (Hubalek & Halouzka, 1999).…”