The niche of One Health approaches in Lassa fever surveillance and control.

Lassa fever (LF), a zoonotic illness, represents a public health burden in West African countries where the Lassa virus (LASV) circulates among rodents. Human exposure hinges significantly on LASV ecology, which is in turn shaped by various parameters such as weather seasonality and even virus and rodent-host genetics. Furthermore, human behaviour, despite playing a key role in the zoonotic nature of the disease, critically affects either the spread or control of human-to-human transmission. Previous estimations on LF burden date from the 80s and it is unclear how the population expansion and the improvement on diagnostics and surveillance methods have affected such predictions. Although recent data have contributed to the awareness of epidemics, the real impact of LF in West African communities will only be possible with the intensification of interdisciplinary efforts in research and public health approaches. This review discusses the causes and consequences of LF from a One Health perspective, and how the application of this concept can improve the surveillance and control of this disease in West Africa.

Phylogeography of Lassa Virus in Nigeria.

Lassa virus is genetically diverse with several lineages circulating in West Africa. This study aimed at describing the sequence variability of Lassa virus across Nigeria and inferring its spatiotemporal evolution. We sequenced and isolated 77 Lassa virus strains from 16 Nigerian states. The final data set, including previous works, comprised metadata and sequences of 219 unique strains sampled between 1969 and 2018 in 22 states. Most of this data originated from Lassa fever patients diagnosed at Irrua Specialist Teaching Hospital, Edo State, Nigeria. The majority of sequences clustered with the main Nigerian lineages II and III, while a few sequences formed a new cluster related to Lassa virus strains from Hylomyscus pamfi Within lineages II and III, seven and five sublineages, respectively, were distinguishable. Phylogeographic analysis suggests an origin of lineage II in the southeastern part of the country around Ebonyi State and a main vector of dispersal toward the west across the Niger River, through Anambra, Kogi, Delta, and Edo into Ondo State. The frontline of virus dispersal appears to be in Ondo. Minor vectors are directed northeast toward Taraba and Adamawa and south toward Imo and Rivers. Lineage III might have spread from northern Plateau State into Kaduna, Nasarawa, Federal Capital Territory, and Bauchi. One sublineage moved south and crossed the Benue River into Benue State. This study provides a geographic mapping of lineages and phylogenetic clusters in Nigeria at a higher resolution. In addition, we estimated the direction and time frame of virus dispersal in the country.IMPORTANCE Lassa virus is the causative agent of Lassa fever, a viral hemorrhagic fever with a case fatality rate of approximately 30% in Africa. Previous studies disclosed a geographical pattern in the distribution of Lassa virus strains and a westward movement of the virus across West Africa during evolution. Our study provides a deeper understanding of the geography of genetic lineages and sublineages of the virus in Nigeria. In addition, we modeled how the virus spread in the country. This knowledge allows us to predict into which geographical areas the virus might spread in the future and prioritize areas for Lassa fever surveillance. Our study not only aimed to generate Lassa virus sequences from across Nigeria but also to isolate and conserve the respective viruses for future research. Both isolates and sequences are important for the development and evaluation of medical countermeasures to treat and prevent Lassa fever, such as diagnostics, therapeutics, and vaccines.

Ebola Virus Epidemiology and Evolution in Nigeria.

Containment limited the 2014 Nigerian Ebola virus (EBOV) disease outbreak to 20 reported cases and 8 fatalities. We present here clinical data and contact information for at least 19 case patients, and full-length EBOV genome sequences for 12 of the 20. The detailed contact data permits nearly complete reconstruction of the transmission tree for the outbreak. The EBOV genomic data are consistent with that tree. It confirms that there was a single source for the Nigerian infections, shows that the Nigerian EBOV lineage nests within a lineage previously seen in Liberia but is genetically distinct from it, and supports the conclusion that transmission from Nigeria to elsewhere did not occur.

Temporal and spatial analysis of the 2014-2015 Ebola virus outbreak in West Africa.

West Africa is currently witnessing the most extensive Ebola virus (EBOV) outbreak so far recorded. Until now, there have been 27,013 reported cases and 11,134 deaths. The origin of the virus is thought to have been a zoonotic transmission from a bat to a two-year-old boy in December 2013 (ref. 2). From this index case the virus was spread by human-to-human contact throughout Guinea, Sierra Leone and Liberia. However, the origin of the particular virus in each country and time of transmission is not known and currently relies on epidemiological analysis, which may be unreliable owing to the difficulties of obtaining patient information. Here we trace the genetic evolution of EBOV in the current outbreak that has resulted in multiple lineages. Deep sequencing of 179 patient samples processed by the European Mobile Laboratory, the first diagnostics unit to be deployed to the epicentre of the outbreak in Guinea, reveals an epidemiological and evolutionary history of the epidemic from March 2014 to January 2015. Analysis of EBOV genome evolution has also benefited from a similar sequencing effort of patient samples from Sierra Leone. Our results confirm that the EBOV from Guinea moved into Sierra Leone, most likely in April or early May. The viruses of the Guinea/Sierra Leone lineage mixed around June/July 2014. Viral sequences covering August, September and October 2014 indicate that this lineage evolved independently within Guinea. These data can be used in conjunction with epidemiological information to test retrospectively the effectiveness of control measures, and provides an unprecedented window into the evolution of an ongoing viral haemorrhagic fever outbreak.

Hospital-based surveillance for Lassa fever in Edo State, Nigeria, 2005-2008.

OBJECTIVES: To estimate the burden of Lassa fever in northern and central Edo, a state in south Nigeria where Lassa fever has been reported. METHODS: Blood samples were obtained from 60 patients hospitalised at the Irrua Specialist Teaching Hospital (ISTH), Irrua, with a clinical suspicion of Lassa fever and from 451 febrile outpatients seen at the ISTH and hospitals in Ekpoma, Iruekpen, Uromi, Auchi and Igarra. All samples were tested retrospectively by Lassa virus-specific RT-PCR. Outpatients were additionally screened for Lassa virus-specific antibodies by indirect immunofluorescent antibody assay. RESULTS: Lassa virus was detected in 25 of 60 (42%) patients with a clinical suspicion of Lassa fever. The disease affected persons of all age groups and with various occupations, including healthcare workers. The clinical picture was dominated by gastrointestinal symptoms. The case fatality rate was 29%. Lassa virus was detected in 2 of 451 (0.44%) febrile outpatients, and 8 (1.8%) were positive for Lassa virus-specific IgG. CONCLUSIONS: Lassa fever contributes to hospital mortality in Edo State. The low prevalence of the disease among outpatients and the low seroprevalence may indicate that the population-level incidence is not high. Surveillance for Lassa fever should focus on the hospitalised patient.

Epizootic emergence of Usutu virus in wild and captive birds in Germany.

This study aimed to identify the causative agent of mass mortality in wild and captive birds in southwest Germany and to gather insights into the phylogenetic relationship and spatial distribution of the pathogen. Since June 2011, 223 dead birds were collected and tested for the presence of viral pathogens. Usutu virus (USUV) RNA was detected by real-time RT-PCR in 86 birds representing 6 species. The virus was isolated in cell culture from the heart of 18 Blackbirds (Turdus merula). USUV-specific antigen was demonstrated by immunohistochemistry in brain, heart, liver, and lung of infected Blackbirds. The complete polyprotein coding sequence was obtained by deep sequencing of liver and spleen samples of a dead Blackbird from Mannheim (BH65/11-02-03). Phylogenetic analysis of the German USUV strain BH65/11-02-03 revealed a close relationship with strain Vienna that caused mass mortality among birds in Austria in 2001. Wild birds from lowland river valleys in southwest Germany were mainly affected by USUV, but also birds kept in aviaries. Our data suggest that after the initial detection of USUV in German mosquitoes in 2010, the virus spread in 2011 and caused epizootics among wild and captive birds in southwest Germany. The data also indicate an increased risk of USUV infections in humans in Germany.

Current molecular epidemiology of Lassa virus in Nigeria.

Recent Lassa virus strains from Nigeria were completely or partially sequenced. Phylogenetic analysis revealed the predominance of lineage II and III strains, the existence of a previously undescribed (sub)lineage in Nigeria, and the directional spread of virus in the southern part of the country. The Bayesian analysis also provided estimates for divergence times within the Lassa virus clade.

Improved detection of Lassa virus by reverse transcription-PCR targeting the 5' region of S RNA.

The method of choice for the detection of Lassa virus is reverse transcription (RT)-PCR. However, the high degree of genetic variability of the virus poses a problem with the design of RT-PCR assays that will reliably detect all strains. Recently, we encountered difficulties in detecting some strains from Liberia and Nigeria in a commonly used glycoprotein precursor (GPC) gene-specific RT-PCR assay (A. H. Demby, J. Chamberlain, D. W. Brown, and C. S. Clegg, J. Clin. Microbiol. 32:2898-2903, 1994), which prompted us to revise the protocol. The design of the new assay, the GPC RT-PCR/2007 assay, took into account 62 S RNA sequences from all countries where Lassa fever is endemic, including 40 sequences generated from the strains in our collection. The analytical sensitivity of the new assay was determined with 11 strains from Sierra Leone, Liberia, Ivory Coast, and Nigeria by probit analysis; the viral loads detectable with a probability of 95% ranged from 342 to 2,560 S RNA copies/ml serum, which corresponds to 4 to 30 S RNA copies/assay. The GPC RT-PCR/2007 assay was validated with 77 serum samples and 1 cerebrospinal fluid sample from patients with laboratory-confirmed Lassa fever. The samples mainly originated from Liberia and Nigeria and included strains difficult to detect in the assay of 1994. The GPC RT-PCR/2007 assay detected virus in all clinical specimens (100% sensitivity). In conclusion, a new RT-PCR assay, based in part on the protocol developed by Demby et al. in 1994, for the detection of Lassa virus is described. Compared to the assay developed in 1994, the GPC RT-PCR/2007 assay offers improved sensitivity for the detection of Liberian and Nigerian Lassa virus strains.

Associated risk factors and pulsed field gel electrophoresis of nasal isolates of Staphylococcus aureus from medical students in a tertiary hospital in Lagos, Nigeria.

Staphylococcus aureus infections are growing problems worldwide with important implications in hospitals. The organism is normally present in the nasal vestibule of about 35% of apparently healthy individuals and its carriage varies between different ethnic and age groups. Staphylococcal nasal carriage among health workers is particularly important to establish new clones and track origin of infections during outbreak situations. To determine the carriage rate and compare the pulsed field gel patterns of the strains, nasal swabs were collected from 185 medical students in a teaching hospital in Lagos, Nigeria. Isolates of S. aureus were tested for heamolysin production, methicillin sensitivity and Pulsed Field Gel Electrophoresis (PFGE) was performed. The results showed S.aureus nasal carrier rate of 14% with significant rate among males compared to females. All the isolates produced heamolysin. Antibiotic susceptibility pattern revealed that majority of the isolates was susceptible. Five strains (19%) harboured resistant determinants to penicillin and tetracycline. None of the strains was resistant to methicillin. 44% of the isolates typed by PFGE had type B, the most predominant pulsotype. PFGE A clone exhibited a single resistance phenotype suggesting a strong clonal relationship that could punctual an outbreak in the hospital. The results speculate that nasal carriage among medical personnel could be a function of various risk factors. Personal hygiene and behaviour may however be the means to reducing colonization and spread of S.aureus in our hospitals.

Associated risk factors and pulsed field gel electrophoresis of nasal isolates of Staphylococcus aureus from medical students in a tertiary hospital in Lagos, Nigeria

Staphylococcus aureus infections are growing problems worldwide with important implications in hospitals. The organism is normally present in the nasal vestibule of about 35 percent of apparently healthy individuals and its carriage varies between different ethnic and age groups. Staphylococcal nasal carriage among health workers is particularly important to establish new clones and track origin of infections during outbreak situations. To determine the carriage rate and compare the pulsed field gel patterns of the strains, nasal swabs were collected from 185 medical students in a teaching hospital in Lagos, Nigeria. Isolates of S. aureus were tested for heamolysin production, methicillin sensitivity and Pulsed Field Gel Electrophoresis (PFGE) was performed. The results showed S.aureus nasal carrier rate of 14 percent with significant rate among males compared to females. All the isolates produced heamolysin. Antibiotic susceptibility pattern revealed that majority of the isolates was susceptible. Five strains (19 percent) harboured resistant determinants to penicillin and tetracycline. None of the strains was resistant to methicillin. 44 percent of the isolates typed by PFGE had type B, the most predominant pulsotype. PFGE A clone exhibited a single resistance phenotype suggesting a strong clonal relationship that could punctual an outbreak in the hospital. The results speculate that nasal carriage among medical personnel could be a function of various risk factors. Personal hygiene and behaviour may however be the means to reducing colonization and spread of S.aureus in our hospitals.