A sero-epidemiological survey for Bunyaviridae and certain other arboviruses in Pakistan

Complement fixation test reactions to the following viruses were studied in 372 samples (157 rodents, 172 domestic animals, 43 persons) from Pakistan: Bunyaviridae, Phlebovirus: Phlebotomus fever Sicilian (PFS), Phlebotomus fever Naples (PFN), Karimabad (KAR), Salehabad (SAL); Nairovirus: Crimean-Congo haemorrhagic fever (CCHF), Hazara (HAZ), Dera Ghazi Khan (DGK), Dhori (DHO); Uukuvirus: Manawa (MWA); "possible members": Bakau (BAK), Bhanja (BHA). Reoviridae, Orbivirus: Wad Medani (WM). Unclassified: Wanowrie (WAN). Four of these viruses are Phlebotomus-borne (PFS, PFN, KAR, SAL). The other nine ar tick-borne. Antibodies against each virus were detected in sera from rodents. Antibodies against PFS, PFN, KAR, CCHF, DGK, BHA, WM and WAN viruses were detected in sera from domestic animals. Antibodies against PFS, CCHF, DGK, DHO, MWA, BHA, and BHA and WAN viruses were detected in human sera. The presence in Pakistan of KAR, DHO, BHA, and WAN viruses is documented for the first time. Over-all prevalence rates were highest for BHA (12.1%) and WM (10.7%) viruses, followed by DGK, CCHF, PFN and PFS (4.0 to 5.4%) and DHO, KAR, WAN, SAL, MWA, BAK and HAZ (0.3 to 2.1%). Epidemiological factors relating to virus circulation and human disease are discussed.     

Prevalence of antibodies to Japanese encephalitis and West Nile viruses among wild birds in the Krishna-Godavari Delta,Andhra Pradesh,India

In the Krishna-Godavari Delta region of the State of Andhra Pradesh, India, 866 sera obtained from trapped birds of 13 species were tested for neutralizing antibody to Japanese encephalitis (JE) virus; two species of birds belonging to the family Ardeidae, Ardeola grayii (pond heron) and Bubulcus ibis (cattle egret), contributed 514 of these sera. Neutralizing antibody to JE virus—i.e. sera giving positive reactions—was detected in 179 sera (34·8%) from these two species; in addition, two sera (0·4%) gave equivocal reactions, presumably indicating partial protection. There were only nine positive reactors (2·6%) among the remaining 352 sera from all other bird species. Of the 181 sera from ardeid birds in which neutralizing activity was detected, 174 were tested for neutralizing antibody to West Nile (WN) virus. The results indicated that 35·6% of these 179 sera had antibody specific to JE virus only and 63·8% possessed neutralizing antibodies to JE virus or to WN virus or to both; these figures represent 12·5% and 22·5%, respectively, of the total of 514 birds of these two species which were tested for neutralizing antibody to JE virus. The findings suggest that ardeid birds may be involved in the natural cycle of JE virus and, possibly, also of WN virus in India.     

我国一些地区人血清的虫媒病毒抗体调查

本文调查了28个省、市、自治区的人血清对18种虫媒病毒抗原的血凝抑制抗体,发现我国广大地区主要存在乙组虫媒病毒,但也存在甲组和布尼安病毒的可能。甲组病毒的抗体阳性数占总阳性数的16.7%(58/347),新疆、青海、黑龙江、山西、福建、甘肃省占甲组虫媒病毒抗体阳性数的84%。布尼安病毒中特别是Aino病毒的抗体阳性率较高,占总阳性数的12.7%(45/347),黑龙江8/10人阳性,其HI滴度都大于1/80,最高为1/1280,平均滴度为1/320,黑龙江、新疆、福建、北京占布尼安总阳性数的70%。乙组虫媒病毒则以乙脑为主。但其它病毒的抗体如Zika、 Kunjin的抗体阳性也很高,故推测我国除已知有乙脑、森脑、登革热外,尚有其它乙组虫媒病毒存在的可能。     

West Nile virus in Pakistan. 1. Sero-epidemiological studies in Punjab Province

Serum samples collected during 1978–1979 from residents of the Chiniot and Changa Manga National Forest (CMF) areas of Punjab Province, Pakistan, had over-all neutralizing (N) antibody positive rates for West Nile (WN) virus of 32·8% (n = 192) and 38·5% (n = 239), respectively. Comparison of the age-specific antibody rates indicated that the pattern of exposure to infection was different in the two areas. Samples from a 1968 serosurvey of residents of the CMF area had an age-specific N antibody profile similar to the 1978 CMF sample, but both the over-all N and haemagglutinationinhibition (HI) antibody positive rates were much higher in the 1968 sample. When tested against antigen prepared from the Pakistan I-746 strain of WN virus, the percentage of sera HI antibody positive and the geometric mean titre of the sera were significantly higher than when tested against the Egypt-101 antigen. One of 124 and 11 of 50 sera from the 1978 and 1968 samples from CMF exhibited detectable HI antibody against dengue-3 virus, respectively, indicating cross-reacting flavivirus antibody was present. None of the positive sera had a higher titre against dengue-3 than against WN virus, but four of the 1968 sera reacted to equal titre against both antigens.During the 1978–1979 CMF survey, serum samples from domestic and wild animals were tested for WN virus antibody. Of the 317 wild birds captured, 85 were N-antibody positive. The only frequently bled mammal was the Indian cow, from which 21 of 58 samples were positive for WN antibody.     

Antibodies to certain arboviruses in humans from a flooded village in Egypt

A study was carried out on 180 sera collected from inhabitants of a seepage flooded village (Begiram) in a Nile Delta governorate in Egypt. The aim of the study was to monitor the prevalence of certain arboviruses; some of them are known to be endemic in Egypt. Sera were screened by ELISA except for the HTN by IF, and the results indicated that WN and SFS exhibited the highest prevalence 45.5% followed by SFN (21%). These 3 viruses are known to be endemic in Egypt. The high prevalence of W.N. and S.F.S viruses in Begiram village in comparison to lower rates detected in sera from nearby Sharkqiya governorate collected almost at the same time may reflect the adverse effect of the environmental change in the flooded village. RNF virus which caused a major epidemic in Egypt in 1977 and continued to be circulating until 1980, its antibodies were detected only in those above 20 years of age with a prevalence rate of 5%. Antibodies against two tick borne viruses viz QRF and CCHF were also detected with low prevalence rate 2.75% and 1.1% respectively; also antibodies to the rodent-borne HTN virus were detected with prevalence rate 1.1%. Antibodies to mosquito borne SIN and BAT viruses were not detected in the tested sera.     

Neutralizing antibody response to Japanese encephalitis inactivated mouse brain vaccine among laboratory personnel

Among vaccinees given two doses of JE Nakayama strain liquid vaccine, 41.8% had significant neutralizing (N) antibody response to the P20778 strain and 48.6% to the Japanese Nakayama strain. Among vaccinees who received three doses of the freeze-dried vaccine, the proportion of positive reactors was 53.8% when the sera were tested with the P20778 strain and 47.4% with the Nakayama strain. A fairly large proportion of those vaccinees who had responded positively to the latter vaccine were found to have lost detectable N antibodies to the P20778 strain and a smaller proportion to the Nakayama strain 13 to 17 months after the third dose of vaccine. Following the administration of a booster dose of the vaccine after this time interval, 65.2% and 56.5% of vaccinees responded positively to the P20778 strain and the Nakayama strain, respectively. The differences between the proportion of positive reactors to the two strains were not significant either for the liquid vaccine or the freeze-dried vaccine. An important finding was the priming effect of infection with West Nile (WN) virus before vaccination. Those vaccinees who had N antibody to WN virus before vaccination had a significantly higher N antibody response to the P20778 strain of JE virus than those who had no detectable antibody to WN virus. These findings indicate that the JE Nakayama strain vaccine would be efficacious in India, particularly in view of the widespread prevalence of WN virus infection.     

Antibodies against haemorrhagic fever viruses in Kenya populations

Human sera from Lodwar (77 sera), Nzoia (841 sera), Masinga (251 sera), Laisamis (174 sera) and the Malindi/Kilifi area (556 sera) in Kenya were tested by indirect immunofluorescence for antibodies against Marburg, Ebola (Zaire and Sudan strains), Congo haemorrhagic fever, Rift Valley fever and Lassa viruses. Antibodies against Ebola virus, particularly the Zaire strain, were detected in all regions and were, over-all, more abundant than antibodies against the other antigens. Ebola and Marburg antibody prevalence rates were highest in the samples from Lodwar and Laisamis, both semi-desert areas. Antibodies against Rift Valley fever virus were also highest in the Lodwar sample followed by Malindi/Kilifi and Laisamis. Congo haemorrhagic fever virus antibodies were rare and no antibodies against Lassa virus were detected in the 1899 sera tested.     

Exposure to rodents and rodent-borne viruses among persons with elevated occupational risk

Persons who have frequent contact with rodents as part of their occupation may be at increased risk of exposure to rodent-borne viruses such as Sin Nombre virus (SNV), the agent of hantavirus pulmonary syndrome, and Whitewater Arroyo virus (WWA), a New World arenavirus. Eighty-one persons with possible occupational exposure to rodents completed questionnaires and provided specimens for serologic testing. Seventy-two participants reported handling rodents as part of their job. The mean total number of rodents handled during participants' careers was approximately 2200. IgG antibody to lymphocytic choriomeningitis virus was detected in serum from one (1.2%) participant. IgG antibody to SNV, WWA, and Amapari viruses was not detected in any of the serum specimens. Despite considerable exposure to rodents, participants did not have significant serological evidence of exposure to rodent-borne viruses.     

Virologic and serologic investigations of West Nile virus circulation in Belarus

In 1985-1994 virologic and serologic investigations were performed for the purposes of West Nile (WN) virus circulation establishment on the territory of Belarus. Blood-sucking mosquitoes, midges, wild small mammals, birds as well as blood and cerebrospinal samples from patients with nondifferentiated fevers and from healthy individuals were under studies. Four virus strains were isolated in Belarus for the first time, namely: 1--from birds (48-WN Tremlya); 2--from Aedes mosquitoes (319 and 2438); 1--from a febrile patient (Win). Their antigenic and biological properties were examined in cell cultures and laboratory animals. The isolates turned to be identical with each other and closely related to reference Egypt strain Eg 101, that is a topotype for the African virus group. One more WN virus strain (8891) was isolated from Anopheles mosquitoes in 1999. Specific antibodies to the virus in human blood sera were identified by immunological and serologic assays in 1.7% of Belarusian population. In Gomel and Brest Regions the percentage of seropositive individuals reached 5.8 and 15.4, respectively. WN virus antibodies prevailed in 0.6-5.8% of cattle, in 2.9-6.8% of wild small mammals and in 6.5-16.7% of birds. Thus, the conclusion was made on the existence of favourable conditions for the virus spread throughout the whole country and in the south in particular. Blood-sucking mosquitoes and birds are principle vectors in WN virus circulation in Belarus. 16 serologically confirmed cases of WN encephalitis were revealed in patients with fever of obscure etiology. In the view of the given data, reports on the reemergence of the pathogen in different countries and the tendency in global warming WN virus monitoring should become a subject of concern for Belarusian public medical care services.     

Chimeric West Nile/dengue virus vaccine candidate: preclinical evaluation in mice, geese and monkeys for safety and immunogenicity

A live attenuated virus vaccine is being developed to protect against West Nile virus (WN) disease in humans. Previously, it was found that chimeric West Nile/dengue viruses (WN/DEN4 and WN/DEN4Delta30) bearing the membrane precursor and envelope protein genes of WN on a backbone of dengue type 4 virus (DEN4) with or without a deletion of 30 nucleotides (Delta30) in the 3' noncoding region of the DEN4 part of the chimeric genome were attenuated and efficacious in mice and monkeys against WN challenge. Here, we report the generation of a clinical lot of WN/DEN4Delta30 virus and its further preclinical evaluation for safety and immunogenicity in mice, geese and monkeys. The vaccine candidate had lost neuroinvasiveness in highly sensitive immunodeficient mice inoculated intraperitoneally and had greatly reduced neurovirulence in suckling mice inoculated intracerebrally (IC). Compared to the wild-type WN parent, the chimeric virus was highly restricted in replication in both murine and human neuroblastoma cells as well as in brains of suckling mice. The WN/DEN4Delta30 virus failed to infect geese, indicating that chimerization of WN with DEN4 completely attenuated WN for this avian host. This observation suggests that the WN/DEN4 chimeric viruses would be restricted in their ability to be transmitted from vaccinees to domestic or wild birds. In monkeys, the WN/DEN4Delta30 vaccine candidate was highly immunogenic despite its low level of replication with undetectable viremia. Furthermore, the WN/DEN4Delta30 vaccine virus was safe and readily induced neutralizing antibodies against WN in monkeys immune to each of the four serotypes of dengue virus. These studies confirm the attenuation of WN/DEN4Delta30 for non-human primates, including dengue-immune monkeys, and demonstrate both a highly restricted replication (>10(8)-fold decrease) in the brain of mice inoculated IC and an absence of infectivity for birds, findings that indicate this vaccine should be safe for both the recipient and the environment.     

Mosquitoborne viruses, Czech Republic, 2002

Specimens from residents (N = 497) of an area affected by the 2002 flood were examined serologically for mosquitoborne viruses. Antibodies were detected against Tahyna (16%), Sindbis (1%), and Batai (0.2%) viruses, but not West Nile virus. An examination of paired serum samples showed 1 Tahyna bunyavirus (California group) infection.     

Studies on arboviruses in Egypt: II. Contribution of arboviruses to the aetiology of undiagnosed fever among children

Acute blood samples from 120 children, attending the fever hospital in Alexandria and complaining of fever, were collected and examined for haemagglutination-inhibiting (HAI) and complement-fixing (CF) antibodies against the following arbovirus antigens; Sindbis, West Nile (WN), yellow fever, dengue 1, sandfly fever, Quaranfil, Chenuda and Nyamanini. Positive reactions in the acute sera were only detected against Sindbis (4·3%) and WN (4·3%) antigens. The convalescent sera obtained from 48 of these children showed a pronounced HAI titre against WN antigen in 14·6% of them. The same sera showed a lower titre against yellow fever antigen (Asibi strain) which is due to cross-reaction between the two viruses. None of the acute or the convalescent sera showed CF antibodies against Quaranfil, Chenuda or Nyamanini antigens. The convalescent sera were not tested against dengue type 1 antigen. It is suggested that of the known arboviruses in Egypt, WN is the most important from the public health point of view.     

Mosquito-borne arboviruses in Norway: further isolations and detection of antibodies to California encephalitis viruses in human, sheep and wildlife sera.

Seven virus strains antigenically related to the California encephalitis (CE) virus group were isolated from Norwegian Aedes spp. mosquitoes collected in 1976. So far CE viruses have been isolated from five different Aedes spp. in Norway. Furthermore, two virus strains related to the Bunyamwera group were isolated from Anopheles claviger. Antibodies to CE viruses were demonstrated in 22% of 1014 military recruits tested. Among 91 soldiers who were monitored by monthly blood samples during the mosquito season, seroconversions were detected in 11 individuals. Specific IgM antibodies were found in seven of them. Disease symptoms in connexion with the CE virus infections were not seen. The prevalence of CE antibodies in patients with CNS or respiratory infections was not higher than in control groups. Seroconversions were not seen in any of the groups. Screening of sheep sera from six different areas in northern Norway indicated significantly different degrees of CE virus activity. Passerine birds may be important CE virus hosts, while small rodents seem unimportant. Specific IgM antibodies were detected in the sera of one of three hares and one of two squirrels. Of the methods used, single radial haemolysis (SRH) and immuno-electro-osmophoresis (IEOP) seemed to be well suited for serological screenings. However, an indirect immunofluorescence antibody test (IFAT) which was used may be an attractive alternative if high-quality anti-species conjugates are available. The haemagglutination-inhibition (HI) test used gave a high number of false positive results.     

Mosquito-borne arboviruses in Norway: further isolations and detection of antibodies to California encephalitis viruses in human, sheep and wildlife sera

Seven virus strains antigenically related to the California encephalitis (CE) virus group were isolated from Norwegian Aedes spp. mosquitoes collected in 1976. So far CE viruses have been isolated from five different Aedes spp. in Norway. Furthermore, two virus strains related to the Bunyamwera group were isolated from Anopheles claviger. Antibodies to CE viruses were demonstrated in 22% of 1014 military recruits tested. Among 91 soldiers who were monitored by monthly blood samples during the mosquito season, seroconversions were detected in 11 individuals. Specific IgM antibodies were found in seven of them. Disease symptoms in connexion with the CE virus infections were not seen. The prevalence of CE antibodies in patients with CNS or respiratory infections was not higher than in control groups. Seroconversions were not seen in any of the groups. Screening of sheep sera from six different areas in northern Norway indicated significantly different degrees of CE virus activity. Passerine birds may be important CE virus hosts, while small rodents seem unimportant. Specific IgM antibodies were detected in the sera of one of three hares and one of two squirrels. Of the methods used, single radial haemolysis (SRH) and immuno-electro-osmophoresis (IEOP) seemed to be well suited for serological screenings. However, an indirect immunofluorescence antibody test (IFAT) which was used may be an attractive alternative if high-quality anti-species conjugates are available. The haemagglutination-inhibition (HI) test used gave a high number of false positive results.     

Evidence for flavivirus(es) outside of the distribution area for Ixodes ricinus in Norway.

Small rodent (vole) sera were collected from three different locations in Norway. One of these was within the distribution area for Ixodes ricinus, and a tick-borne encephalitis (TBE) virus strain had been isolated from ticks collected there (Traavik & Mehl, 1977). The two other locations were outside the I. ricinus area, one in southern Norway, the other at nearly 70 degrees N. The sera were tested for TBE antibodies by hemagglutination inhibition (HI), hemolysis-in-gel (HIG) and complement fixation (CFT). All sera were also tested for HI antibodies to Uukuniemi (UUK) virus, and some positive TBE HI reactions were verified by separation of immunoglobulins and serum lipoproteins in NaBr gradients. Animals containing TBE virus antibodies reacting in all three serological tests and animals with UUK HI antibodies were detected only from the location within the I. ricinus area. From the two locations outside the I. ricinus area we found animals which had antibodies reacting with TBE virus in HI and HIG, but not in CFT. Antibodies to UUK were not detected. The results indicate that flavivirus(es) related to, but not identical with TBE viruses are transmitted by other vectors than I. ricinus in parts of Norway.     

Serological evidence of Hantaan-related viruses in Hong Kong

Sera from rats (Rattus norvegicus), domestic animals and man in Hong Kong were studied by immunofluorescent antibody assay and plaque reduction neutralization tests for evidence of infection by Hantaan-related viruses. Antibody probably arising from infection by Seoul or a Seoul-like virus was detected in rat and human sera (and one pig serum), highlighting the potential public health importance of this group of viruses in Hong Kong, and in the region.     

云南省西南边境地区人血清虫媒病毒抗体调查

本文报告了云南省西南部4个专州9个县的760份人血清对11种虫媒病毒抗原的血凝抑制抗体检查结果,发现不仅乙脑和登革抗体较普遍,同时也存在其它黄病毒组和甲组虫媒病毒的抗体。
甲组虫媒病毒抗体阳性率平均为36.18%(275/760),其中MAY阳性率最高占总阳性数的68.73%(189/275),其次是CHIK占22.18%(61/275),几何平均滴度(GMT),VEE为164.4,MAY为94.48,CHIK为66.7。有交叉反应的血清178份,占64.73%.
黄病毒组抗体阳性率为77.37%(588/760),其中登革和乙脑阳性率最高,前者为36.58%(278/760,后者为27.89%(212/760),其它病毒的阳性率分别为:KFD22.24%(169/760),MVE22.11%(168/760),KUN18.68%(142/760),POW8.82%(67/760),LGT7.89%(60/760)。黄病毒抗体检查中重复感染者较多,占检查数的33.03%(251/760),占黄病毒组总阳性数的42.69%(251/588)。抗体滴度在1:640以上者有403人,占总阳性人次数的36.64%(403/1100),几何平均滴度为355.8。组内交叉反应率达97.09%。     

Evidence for flavivirus(es) outside of the distribution area for Ixodes ricinus in Norway

Small rodent (vole) sera were collected from three different locations in Norway. One of these was within the distribution area for Ixodes ricinus, and a tick-borne encephalitis (TBE) virus strain had been isolated from ticks collected there (Traavik & Mehl, 1977). The two other locations were outside the I. ricinus area, one in southern Norway, the other at nearly 70 degrees N. The sera were tested for TBE antibodies by hemagglutination inhibition (HI), hemolysis-in-gel (HIG) and complement fixation (CFT). All sera were also tested for HI antibodies to Uukuniemi (UUK) virus, and some positive TBE HI reactions were verified by separation of immunoglobulins and serum lipoproteins in NaBr gradients. Animals containing TBE virus antibodies reacting in all three serological tests and animals with UUK HI antibodies were detected only from the location within the I. ricinus area. From the two locations outside the I. ricinus area we found animals which had antibodies reacting with TBE virus in HI and HIG, but not in CFT. Antibodies to UUK were not detected. The results indicate that flavivirus(es) related to, but not identical with TBE viruses are transmitted by other vectors than I. ricinus in parts of Norway.     

Serological survey of Prospect Hill virus infection in indigenous wild rodents in the USA

We found serological evidence of infection with Prospect Hill virus, a Hantaan-like virus isolated from meadow voles (Microtus pennsylvanicus), in microtine and cricetid rodents trapped in Maryland, West Virginia, Minnesota and California, USA. Fluorescent antibodies were detected in sera from M. pennsylvanicus (74/277), M. californicus (39/185), Clethrionomys gapperi (5/51), Peromyscus maniculatus (4/22) and P. truei (1/11). Sera from seropositive P. maniculatus contained neutralizing antibodies against Prospect Hill virus, confirming that infection with Prospect Hill virus or antigenically related viruses is not restricted to microtine rodents in the USA. Despite the widespread distribution of Prospect Hill virus in indigenous rodents, the recent demonstration that American mammalogists are only rarely infected supports the view that the overall risk of Prospect Hill virus infection in man is low.     

Construction and evaluation of a chimeric pseudoinfectious virus vaccine to prevent Japanese encephalitis

Multiple vaccines exist to control Japanese encephalitis (JE), but all suffer from problems. We have developed a new type of flavivirus vaccine, a pseudoinfectious virus (RepliVAX WN) that prevents West Nile virus (WNV)-induced disease. Here, we describe production of a chimeric RepliVAX (RepliVAX JE) that expresses the JE virus (JEV) prM and E proteins. Our prototype RepliVAX JE replicated poorly in cells, but blind passage produced a better-growing derivative, and analyses of this derivative allowed us to engineer a second-generation RepliVAX (RepliVAX JE.2) that grew to high titers. RepliVAX JE.2 elicited neutralizing antibodies in both mice and hamsters and provided 100% protection from a lethal challenge with JEV or WNV, respectively. These results demonstrate the utility our RepliVAX platform for producing a JE vaccine.