Prevalence and association of human parvovirus B19V with hepatitis B and C viruses in Nigeria.

Co-infection of parvovirus B19 with hepatitis B virus has been found in patients with acute and chronic hepatitis. The clinical significance of parvovirus B19 in hepatitis B co-infected patients is still controversial. In this study parvovirus B19 antibodies and DNA were investigated in serum samples from 76 patients with HBV infection, 17 with HBV/HCV co-infection and 44 healthy controls. In the sera from patients with HBV infection, anti-B19V IgM and IgG antibodies were detected in 24/76 (32%) and 25/76 (33%), in 6/17 (35%) and 8/17 (47%) of HBV/HCV co-infected patients, and in 14/44 (32%) and 12/44 (12%) of a non-hepatitis healthy controls, respectively. B19V DNA was detected in 8/76 (11%) of patients with HBV infection and in 3/17 (18%) of patients with a HBV/HCV co-infection, and in 4/44 (9%) healthy controls. The occurrence of parvovirus B19 DNA was significantly higher in patients with symptomatic HBV 4/20 (20%) compared to asymptomatic HBV carrier 4/56 (7%) (P<0.05). Ten of the positive B19V DNA sequences belonged to B19V genotype 1 while two belonged to genotype 3. The results of this study showed a significant difference in the prevalence of parvovirus B19 DNA in symptomatic HBsAg positive as compared to asymptomatic HBsAg positive individuals; however, the conclusion that parvovirus B19 infection increased the frequency of liver disease was not supported. Long-term longitudinal studies are, however, required to determine the synergistic effect of parvovirus B19 infection in HBV or HBV and HCV co-infected persons.

Rabies and antirabies immunization in South Western Nigeria: knowledge, attitude and practice.

Factors responsible for the continued endemicity of rabies in Nigeria were determined by carrying out a knowledge, attitude and practice study among residents of Osun State. Structured questionnaires were administered to 679 individuals comprising students, traders and civil servants. Only 33.4% of the respondents knew rabies could be prevented by vaccination, while 38.7% believed that the infection could be treated with herbs. Of the 387 victims of dog bite, 240 (62%) never sought prophylactic postexposure treatment. Of the 10 people who received postexposure treatment, only one received the appropriate treatment consisting of washing, disinfection of wounds, tetanus toxoid and complete antirabies immunization.

Absence of HIV-1 and HIV-2 seroconversions in a cohort medical students in a Nigerian medical school.

A cohort of 70, HIV-1 and HIV-2 seronegative medical students were followed up for 30 months, after which 65 were retested for HIV antibody. None of the students was infected by HIV during the period of study. A questionnaire survey carried out showed that all the students had a very good knowledge of HIV, its mode of transmission, control and prevention. Most of the students have never had sex or had a single sex partner and used condoms always or most of the time during sexual intercourse.

An epidemiological study of rotavirus diarrhoea in a cohort of Nigerian infants: I. Methodology and experiences in the recruitment and follow-up of patients.

A community-based prospective study was carried out in the city of Ibadan, Nigeria, to determine the epidemiology of rotavirus infection and diarrhoea among children in the first two years of life. Implementation of the proposed study methods was hindered by a number of factors common to large urban areas in developing Africa. These factors included difficulties in recruiting the study sample because of maternal fears, cultural beliefs, and lack of paternal consent. Following recruitment, longitudinal surveillance was made difficult by inefficient telecommunications, a haphazard house numbering system, transportation difficulties, mobility of the population, and lack of incentive for continued participation. Despite these difficulties, 73% of the recruited newborns remained in the study until they reached the age of 12 months. The drop-out rate in the second year of study was higher, largely because fewer incentives could be provided during the second year. This paper reviews the operational considerations of implementing a longitudinal study protocol under these conditions, and discusses the potential impact of these problems and the measures taken to overcome them on the results of this study.

PIP: A review of the methodology and experiences in an epidemiological survey of infant diarrhea in Ibadan, Nigeria is discussed. The survey successfully recruited 131 babies for a study on rotavirus diarrhea. Of those 131 babies, 740 samples were actually collected and 7704 visits were made. Although the actual number of samples, visits and participants was less than anticipated, the survey was considered an achievement in that it was one of very few community-based diarrhea studies in Africa. Those who participated appeared to be less tied to traditions and more educated. Incentives, particularly the distribution of free drugs (antimalarials and haematinics), were important in motivating participation. The reasons for non-participation given by mothers includes: belief and taboos, the influence of their relatives or husbands and lack of education. Despite incentives, zeal and surveillance, only 75% of the babies remained in the study for up to 12 months, obscuring a complete epidemiological picture. Many operation obstacles and compromises occur when a community-based study in a large unplanned population such as this one is attempted.

An epidemiological study of rotavirus diarrhoea in a cohort of Nigerian infants: II. Incidence of diarrhoea in the first two years of life.

In a community-based prospective study of diarrhoeal diseases carried out in Ibadan, 131 infants were selected at birth. The maximum possible length of follow-up ranged from 16 to 24 months. Weekly surveillance for diarrhoea was carried out at home by Primary Health Care workers. Each child was also required to attend a monthly clinic. Of the 131 babies, 95 (73%) completed at least one year of follow-up. All of these had at least one episode of diarrhoea within the first year of life. The incidence rate of diarrhoea in the first year of life was 3.2 cases/child/year. The mean duration of diarrhoea days in the first year of life was 16 per child per year (range 3-34 days). The peak incidence of diarrhoea and the greatest number of diarrhoea days were in the age interval 6-9 months. The mean duration of diarrhoea was five days per episode. Faecal samples for 280 diarrhoea episodes during the first year of life were examined for rotavirus using the ELISA technique: 22 (7.7%) were found to be positive. The mean duration of rotavirus diarrhoea episodes was eight days.

PIP: Researchers studied the incidence of diarrheal diseases in a cohort of 131 infants in Ibadan, Nigeria Primary health care workers visited each infant every week to learn of any diarrheal episodes. In additions, each child was to attend a clinic monthly for further evaluation. Of these infants recruited at birth, 95 (73%) finished 1 year of follow up. The incidence rate for acute diarrhea was 3.2 episodes/child, and each infant experienced at least 1 episode. For those infants aged 6-8 months, the incidence rate was 9 episodes/100 child weeks which was the highest mean incidence rate of all the age groups (ranging from 0-2 months to 18-23 months). In addition, the highest number of diarrhea days/child was for this same age group and it was 5.2 days/child/interval. In the 1st year of life, the mean number of diarrhea days/child/year was 16 (range 3-34) and the mean duration of each episode was 5 days. Additionally, laboratory personnel examined 280 fecal samples from diarrheal episodes for rotavirus. 22 (8%) of these were positive and the majority of these cases occurred in infants 3-5 months old. Rotavirus diarrheal episodes ranged from 5-12 days with a mean of 8 days. 12 (55%) of the infants who tested positive for rotavirus were males, and the mean duration was longer for them (8.4 days) than for the females (7 days), but the difference was not significant. The rotavirus infections caused no deaths. In addition, none of the infants with rotavirus had a 2nd episode of rotavirus infection during the surveillance period.

Arthropod-borne virus antibodies in sera of residents of Kainji Lake Basin, Nigeria 1980.

A survey for haemagglutination-inhibiting arthropod-borne virus antibody was carried out in the Kainji Lake area of Nigeria. Of 267 persons tested, 139 (52%) and 158 (59%) had alphavirus and flavivirus group HI antibody, respectively. The prevalence of antibody to individual virus antigen is as follows: Chikungunya, 45%; Semliki Forest, 25%; Sindbis, 33%, Yellow fever, 31%, Dengue type 2, 46%; and Zika 56%. The presence of high antibody rates to Chikungunya, Dengue type 2 and Yellow fever viruses is of public health significance. These viruses have been identified as the most important arthropod-borne viruses causing human infections in Nigeria.

Dengue virus infections in Nigeria: a survey for antibodies in monkeys and humans.

A retrospective serological survey for dengue immunity was conducted in Nigeria to determine the prevalence of infection in man and non-human primates. Preliminary haemagglutination-inhibition (HI) tests revealed that 63% of persons tested had HI antibodies against one or more of the following flaviviruses: dengue type 1, yellow fever, West Nile and Wesselsbron. Parallel HI and neutralization (N) tests on 179 human sera showed that six of 20 sera (30%) negative for flavivirus HI antibody contained dengue N antibody. This finding emphasized the advantage of the N test over HI in screening for dengue virus immunity. Neutralization tests performed on 1,816 human sera from different geographical locations in Nigeria showed that 45% of Nigerians were immune to dengue type 2 virus. The percentage of immunity in adults aged 20 years and older (51%) was significantly higher than in children (37%) (P less than 0-01). In all four ecological zones sampled, the highest percentage of dengue N antibody was observed in the derived Savannah zone (63%) followed by the rain forest zone (42%). The Southern Guinea savannah and plateau zones had lower percentages of dengue-immune persons. There was a higher prevalence of antibodies in urban (48%) than in rural communities (37%). Tests on dengue-immune sera showed that 35% of such sera contained N antibodies to dengue only or to dengue and one other virus. Therefore, dengue immunity cannot be explained by heterologous cross reactions within the flavivirus group. In addition, evidence of dengue infection was found in monkeys and galagos. 48% of monkeys and 25% of galagos contained dengue N antibody. The presence of specific dengue N antibodies in a few sera suggests that the occurrence of a forest cycle of dengue is possible in Nigeria.

Igbo-Ora virus (an alphavirus isolated in Nigeria): a serological survey for haemagglutination inhibiting antibody in humans and domestic animals.

Sera from humans and animals were tested for antibodies to Igbo-Ora virus by the haemagglutination-inhibition test. Prevalence in the human population (3.6%) was lower than that in the animal population (24.5%) in the same locality. No antibodies were detected in persons less than 20 years of age; the highest prevalence of antibodies was found in those above 40 years old. Among the animal species examined, cattle showed the highest prevalence (40%) of antibodies to Igbo-Ora virus. The potential hazard of the virus to human health is discussed.

Rotavirus infection in children presenting with acute gastroenteritis Ibadan, Nigeria.

Faecal samples from 84 children presenting with acute gastroenteritis at the University College Hospital, Ibadan, Nigeria and 28 from a non-diarrhoeal control group were tested for rotavirus by an ELISA. 18 cases (21%) and none of the controls were positive. Hospital in-patients had a higher percentage of positives (25%) than did out-patients (10%). The age distribution of infections showed that the highest infection rate (67%) occurred in children four to six months old. Percentages of positive samples from other age groups was as follows: 0 to 3 months, 13%; 7 to 12 months, 33%; and 13 to 24 months, 16%. None of the faecal extracts from children older than two years was positive for rotavirus.

Acute bronchiolitis in tropical Africa: a hospital-based perspective in Ibadan, Nigeria.

In a 30-month prospective study of severe acute lower respiratory infections in hospitalized pre-school Nigerian children, acute bronchiolitis was diagnosed in 67 cases; 19 (28.4%) and 2 (3.0%) of these had concomitant pneumonia or croup, respectively. The peak prevalence was in the wet (rainy) season (May-October). The male/female (M:F) ratio in infants < or = 6 months was 2.9:1, differing significantly from the 1.1:1 in older subjects (P = 0.04). None of the subjects had severe malnutrition. Neither a high fever (> or = 39 degrees C), nor tachypnea on admission was significantly correlated with co-existing pneumonia. Of the 29 subjects in whom it was possible to explore viral immunofluorescence studies and/or serodiagnosis, we identified 26 viral identifications in 18 (62.1%) cases; 6 (20.7%) had > or = 2 viruses. Respiratory syncytial virus was identified in 11 (38.0%) of the 29 cases, and parainfluenza virus (PIV) types 1, 2, and 3 in 10 (34.5%). PIV type 3 accounted for 7 cases, including 3 with bacteremia. Bacterial isolates were made in 9 (21.4%) of 42 blood cultures and in the only lung aspirate; Staphylococcus epidermidis and Staphylococcus aureus accounted for 4 and 3 cases, respectively. Although bacteremia was 2.9 times more common in cases with co-existing pneumonia or croup, the respective frequency of virus-positive cases and that of bacteremia was not significantly different between cases with bronchiolitis alone and those with associated pneumonia or croup. No deaths were recorded, but subjects aged > 6 months had a significantly shorter hospital stay than those < 6 months old (P = 0.02). Despite the limited sample size, our findings reflect the etiological importance of the paramyxoviruses and the seasonal pattern of bronchiolitis in tropical Africa.

Preliminary studies on the use of solid-phase immunosorbent techniques for the rapid detection of Wesselsbron virus (WSLV) IgM by haemagglutination-inhibition.

Serum samples from 446 randomly selected persons belonging to different age groups and locations in Nigeria were tested for the presence of WSLV IgM using the flavivirus haemagglutination-inhibition (HI) test adopted to the solid-phase immunosorbent technique (SPIT). 61 (14%) persons had IgM to WSLV only, while 9 (2%) persons had heterologous IgM to WSLV and two other flaviviruses, namely yellow fever and Uganda S viruses. There was a high prevalence of IgM in people of younger age groups than those in older groups. The majority of the IgM positive sera (67 (96%) of the 70 positive sera reacted to high titres (>21:80). With the conventional HI tests, 314 (70%) of the total sera tested had HI antibodies to one or more flaviviruses (yellow fever, West Nile, Potiskum, Zika and Uganda S) out of which 305/314 (97%) had antibodies to 3 or more flaviviruses used in the tests. Although SPIT may not be as sensitive as the conventional HI test, it was found to be more specific and could be adopted for the detection of early WSLV infections in flavivirus hyperendemic environments.

A survey for haemagglutination-inhibiting antibody to West Nile virus in human and animal sera in Nigeria.

A survey for West Nile Virus (WNV) haemagglutination-inhibition (HI) antibody was carried out in humans and domestic animals. Human sera were collected from Ibadan, while the animal sera were collected from both Ibadan and Maiduguri. Out of 304 human sera tested, 123 were positive (40%). There was a higher prevalence of HI antibody in adults than children. Sex distribution of positive sera showed that 37% of males and 43% of females had WNV HI antibody. There was no significant difference in the prevalence of HI antibody in both sexes. On the 123 WNV HI positive sera tested, 104 (85%) and 78 (75%) had yellow fever and Potiskum HI antibody respectively. Monotypic WNV virus reactions were frequently found in children while polytypic reactions were frequently found in adults. A total of 200 animal sera were examined, 50 camels, 50 goats, 49 cattle and 51 sheep. The highest prevalence of HI antibody was found in camels (26%), followed by sheep (20%). Percentage of positive sera in other species were: goat (18%) and cattle (6%). Of the 35 WNV HI positive animal sera, 26 and 20% reacted with Yellow fever and Potiskum virus antigens respectively.

Yellow fever haemagglutination-inhibiting, neutralising and IgM antibodies in vaccinated and unvaccinated residents of Ibadan, Nigeria.

A survey for yellow fever virus haemagglutination inhibiting (HI) and neutralising (N) and IgM antibodies was carried out in unvaccinated people in Ibadan and in those immunised with the yellow fever 17-D vaccine. A total of 207 people were tested for HI antibody to yellow fever and two other flaviviruses namely: Wesselsbron and Uganda S. viruses. Prevalence of HI antibody to each flavivirus antigen was as follows: Yellow fever 26%, Wesselsbron 18% and Uganda S 33%. Of the 207 people, 37 (18%) had yellow fever N antibody. There was a higher prevalence of N antibody to yellow fever virus in adults than children. Twenty-one people vaccinated with 17-D yellow fever vaccine donated post-vaccination sera; 10 (48%) had no prevaccination HI antibody, 7 (33%) had HI antibody to one flavivirus and 4 (19%) to two or more flaviviruses. Ninety percent of seronegative people and all those with prevaccination flavivirus antibodies developed HI or N antibody, following vaccination. A total of 58 unvaccinated people were tested for yellow fever IgM antibody by an enzyme linked immunosorbent assay, 2 (3%) were positive; suggesting that active yellow fever transmission was in progress at the time of survey.

Experimental Rift Valley fever in West African Dwarf sheep.

West African Dwarf sheep were challenged with a low mouse brain-passaged Rift Valley fever virus (Ib-AR 55172) isolated from Nigeria. Viraemia, mild febrile reaction and neutralising antibodies were demonstrated in inoculated animals.

Wesselsbron virus antibody in domestic animals in Nigeria: retrospective and prospective studies.

Retrospective and prospective serological surveys to determine the prevalence of Wesslsbron (WSL) virus infections in animal populations were carried out in different vegetational zones in Nigeria. Sera from 1,492 animals comprising 292 camels, 81 horses, 4 donkeys, 320 cattle, 235 sheep, 260 goats, 114 pigs, 101 dogs and 85 domestic fowls were assayed by haemagglutination-inhibition (HI) test for presence of antibodies to WSL virus and other flavivirus antigens: Yellow Fever (YF), Potiskum (POT), Banzi (BAN), Uganda S (UGS) and West Nile (WN) viruses. Four hundred and eighty one (32%) of the total sera tested were positive for the presence of flavivirus antibodies. The prevalence rates among animals varied with species and vegetational zones of the country. The highest prevalence was noted in animals from a swamp forest zone and was higher among camels, horses, donkeys and sheep when compared with goats, pigs and fowls in different zones. Although monotypic reactions with WSL virus antigen were observed in positive sera, the majority of the WSL virus positive sera cross-reacted with more than two other flavivirus antigens. Serological cross-reactions were most extensive in WSL virus positive horse sera. A ten month sentinel survey among 28 cattle, 68 sheep and 30 goats revealed considerable activity of WSL virus in Nigeria. Of these, 11 cattle and 12 sheep showed antibody conversion to WSL virus antigen. None of the goats seroconverted. Although, there are no records of outbreak of WSL disease in Nigeria, this study revealed that WSL virus is actively circulating among livestock populations in this environment. Flavivirus nucleotide data are needed for final determination of genetic relatedness in this group of viruses.

Antigenic relatedness of selected flaviviruses: study with homologous and heterologous immune mouse ascitic fluids.

The antigenic relationship of 9 flaviviruses, Yellow fever (YF), Wesselsbron (WSL), Uganda S (UGS), Potiskum (POT), West Nile (WN), Banzi (BAN), Zika (ZK), Dengue type 1 (DEN-1) and Dengue type 2 (DEN-2), was assessed by cross-haemagglutination-inhibition (Cross-HI) and cross-complement fixation (Cross-CF) reactions between each of the viruses and their homologous immune mouse ascitic fluids. Titre ratios were calculated using the heterologous and homologous titres. Cross-CF reactions revealed wider antigenic variations among viruses than Cross-HI reactions. There was no significant antigenic variation between WSL, POT and YF viruses using either of those methods. However, definite differences in antigenicity were observed between them and UGS, BAN and ZK viruses. There were no significant differences between UGS, BAN and ZK or between DEN-1 and DEN-2. The serological relationship among flaviviruses is important in establishing diagnosis and epidemiology of these infections in Africa.

Jos virus infection in domestic animals and primates. Pathogenicity and immunological studies.

Three species of domestic animals (rabbits, sheep and goats) and two species of primates Erythrocebus patas monkeys and baboon (Papio anubis) were infected with Jos virus. None of the infected animals developed viraemia or overt clinical disease. Complement-fixing and neutralising antibodies were demonstrated in sera of infected animals.

Potiskum virus: enhancement of replication in a macrophage-like cell line.

Replication of Potiskum virus was studied in P388D1 macrophage-like cell line in the presence and absence of subneutralizing concentrations of specific antiviral antibody. The cultures were infected at multiplicities of infection (MOI) ranging from 0.4 to 0.0004. The virus replicated to high titres at all MOI tested, but there was an enhancement of virus replication in cultures supplemented with the antibody. Enhancement of replication was MOI dependent, the highest ratios being obtained in cultures infected at lowest MOI. In enhancement assays using various dilutions of immune mouse ascitic fluid (IMAF), the highest enhancement ratio was observed at dilution 1 : 500; the enhancing antibody titre was 5,000.

Wesselsbron virus infection in West African dwarf goats (Fouta djallon): virological and immunological studies.

West African dwarf goats were experimentally infected with Nigerian strain of Wesselsbron virus. Viraemia was detected in infected goats 2 days after infection and lasted for one day. A 100% mortality was observed among the infected animals; the virus was reisolated in mice from almost every tissue obtained from the bodies of infected goats. In addition, the infected goats developed complement-fixing and haemagglutination inhibiting antibodies to Wesselsbron virus.

Studies on transmission of Tataguine virus by Culex (pipens) fatigans mosquitoes.

Culex (pipens) fatigans mosquitoes were infected with Tataguine virus by pledget method. Virus was recovered from 40% of mosquitoes that fed on the infective blood meal after 21 days of incubation. Low titres of infective virus were found in the mosquitoes. Tataguine virus was not successfully transmitted to suckling hamsters exposed to the bites of infected mosquitoes.