Impaired lung function in adolescents with pulmonary tuberculosis during treatment and following treatment completion

Background

Little is known about post-tuberculosis lung disease in adolescents. We prospectively assessed lung function in adolescents with microbiologically confirmed pulmonary tuberculosis during treatment and after treatment completion.

Methods

In a prospective study, we enrolled adolescents diagnosed with microbiologically confirmed tuberculosis and healthy tuberculosis-exposed household controls, between October 2020 and July 2021 in Cape Town, South Africa. Spirometry, plethysmography, diffusion capacity lung function tests and 6-min walking test (6MWT) were completed according to international guidelines 2 months into treatment and following treatment completion. Abnormal lung function was defined as abnormal spirometry (z-score < -1.64 for forced expiratory volume in 1 s (FEV1) and/or forced vital capacity (FVC) and/or FEV1/FVC), plethysmography (total lung capacity (TLC) < 80% of predicted, residual volume over TLC of >45%) and/or diffusion capacity (DLCO z-score < -1.64).

Findings

One-hundred adolescents were enrolled; 50 (50%) with tuberculosis and 50 (50%) healthy tuberculosis-exposed controls. Of the 50 adolescents with tuberculosis, ten had multidrug-resistant tuberculosis. Mean age of the group was 14.9 years (SD 2.7), 6 (6.0%) were living with HIV and 9 (9.0%) were previously treated for tuberculosis. Lung function improved over time; during treatment abnormal lung function was found in 76% of adolescents with tuberculosis, compared to 65% after treatment completion. Spirometry indices were lower in adolescents with tuberculosis compared to controls, both at 2 months and after treatment completion. Plethysmography in adolescents with tuberculosis showed that air-trapping was more common during treatment than in controls (12% vs 0%, respectively, p = 0.017); which improved following treatment completion. Adolescents with tuberculosis both during and after treatment completion walked a shorter distance than controls.

Interpretation

Adolescents with tuberculosis have impaired lung function even after treatment completion. It is crucial to include adolescents in trials on the prevention and treatment of tuberculosis-associated respiratory morbidity.

Funding

EDCTP, National Institute of Health, Medical Research Council, BMBF.

UMOYA: a prospective longitudinal cohort study to evaluate novel diagnostic tools and to assess long-term impact on lung health in South African children with presumptive pulmonary TB-a study protocol

BACKGROUND

Despite a high paediatric tuberculosis (TB) burden globally, sensitive and specific diagnostic tools are lacking. In addition, no data exist on the impact of pulmonary TB on long-term child lung health in low- and middle-income countries. The prospective observational UMOYA study aims (1) to build a state-of-the-art clinical, radiological, and biological repository of well-characterised children with presumptive pulmonary TB as a platform for future studies to explore new emerging diagnostic tools and biomarkers for early diagnosis and treatment response; and (2) to investigate the short and long-term impact of pulmonary TB on lung health and quality of life in children.

METHODS

We will recruit up to 600 children (0-13 years) with presumptive pulmonary TB and 100 healthy controls. Recruitment started in November 2017 and is expected to continue until May 2023. Sputum and non-sputum-based samples are collected at enrolment and during follow-up in TB cases and symptomatic controls. TB treatment is started by routine care services. Intensive follow-up for 6 months will allow for TB cases to retrospectively be classified according to international consensus clinical case definitions for TB. Long-term follow-up, including imaging, comprehensive assessment of lung function and quality of life questionnaires, are done yearly up to 4 years after recruitment.

DISCUSSION

The UMOYA study will provide a unique platform to evaluate new emerging diagnostic tools and biomarkers for early diagnosis and treatment response and to investigate long-term outcomes of pulmonary TB and other respiratory events on lung health in children.

Understanding the biology, morbidity and social contexts of adolescent tuberculosis: a prospective observational cohort study protocol (Teen TB)

INTRODUCTION

A considerable burden of the tuberculosis (TB) epidemic is found in adolescents. The reasons for increased susceptibility to TB infection and higher incidence of TB disease in adolescence, compared with the 5-10 years old age group, are incompletely understood. Despite the pressing clinical and public health need to better understand and address adolescent TB, research in this field remains limited.

METHODS AND ANALYSIS

Teen TB is an ongoing prospective observational cohort study that aims to better understand the biology, morbidity and social context of adolescent TB. The study plans to recruit 50 adolescents (10-19 years old) with newly diagnosed microbiologically confirmed pulmonary TB disease and 50 TB-exposed controls without evidence of TB disease in Cape Town, South Africa, which is highly endemic for TB. At baseline, cases and controls will undergo a detailed clinical evaluation, chest imaging, respiratory function assessments and blood collection for viral coinfections, inflammatory cytokines and pubertal hormone testing. At 2 weeks, 2 months and 12 months, TB disease cases will undergo further chest imaging and additional lung function testing to explore the patterns of respiratory abnormalities. At week 2, cases will complete a multicomponent quantitative questionnaire about psychological and social impacts on their experiences and longitudinal, in-depth qualitative data will be collected from a nested subsample of 20 cases and their families.

ETHICS AND DISSEMINATION

The study protocol has received ethical approval from the Stellenbosch University Health Research Ethics Committee (N19/10/148). The study findings will be disseminated through peer-reviewed publications, academic conferences and formal presentations to health professionals. Results will also be made available to participants and caregivers.

Digital health systems strengthening in Africa for rapid response to COVID-19

The COVID-19 pandemic has painfully exposed the constraints of fragile health systems in low- and middle-income countries, where global containment measures largely set by high-income countries resulted in disproportionate collateral damage. In Africa, a shift is urgently needed from emergency response to structural health systems strengthening efforts, which requires coordinated interventions to increase access, efficiency, quality, transparency, equity, and flexibility of health services. We postulate that rapid digitalization of health interventions is a key way forward to increase resilience of African health systems to epidemic challenges. In this paper we describe how PharmAccess' ongoing digital health system interventions in Africa were rapidly customized to respond to COVID-19. We describe how we developed: a COVID-19 App for healthcare providers used by more than 1,000 healthcare facilities in 15 African countries from May-November 2020; digital loans to support private healthcare providers with USD 20 million disbursed to healthcare facilities impacted by COVID-19 in Kenya; a customized Dutch mobile COVID-19 triage App with 4,500 users in Ghana; digital diaries to track COVID-19 impacts on household expenditures and healthcare utilization; a public-private partnership for real-time assessment of COVID-19 diagnostics in West-Kenya; and an expanded mobile phone-based maternal and child-care bundle to include COVID-19 adapted services. We also discuss the challenges we faced, the lessons learned, the impact of these interventions on the local healthcare system, and the implications of our findings for policy-making. Digital interventions bring efficiency due to their flexibility and timeliness, allowing co-creation, targeting, and rapid policy decisions through bottom-up approaches. COVID-19 digital innovations allowed for cross-pollinating the interests of patients, providers, payers, and policy-makers in challenging times, showing how such approaches can pave the way to universal health coverage and resilient healthcare systems in Africa.

Development and analytical validation of a group-specific RT-qPCR assay for the detection of the Simbu serogroup orthobunyaviruses

The Simbu serogroup within the genus Orthobunyavirus belongs to the family Peribunyaviridae and comprises 32 recognised three-segmented negative-sense single-stranded RNA viruses, with a cosmopolitan distribution. This group of arthropod-borne viruses includes important pathogens of humans and domestic animals e.g. Oropouche orthobunyavirus and Schmallenberg virus. Sensitive and specific diagnostic tools are required for recognition and control of outbreaks. A novel TaqMan® RT-qPCR assay was developed, optimised and analytically validated for the broad detection of the Simbu serogroup orthobunyaviruses. A region in the S segment, which encodes the nucleocapsid protein, was used to design a group primer set and a pair of differently labelled TaqMan® minor groove binder probes to distinguish phylogenetic clade A and B of the serogroup. Efficiencies determined for seven members of the group were 99% for Akabane orthobunyavirus (AKAV), 96% for Simbu orthobunyavirus (SIMV), 96% for Shuni orthobunyavirus (SHUV), 97% for Sathuperi orthobunyavirus (SATV), 84% for Shamonda orthobunyavirus (SHAV), 93% for Ingwavuma virus (INGV, now classified as Manzanilla orthobunyavirus) and 110% for Sabo virus (SABOV, now classified as AKAV). The 95% limit of detection (TCID50/reaction) was 10-3.61 for AKAV, 10-2.38 for SIMV, 10-3.42 for SHUV, 10-3.32 for SATV, 10-1.67 for SHAV, 100.39 for INGV and 10-2.70 for SABOV.

Rift valley Fever in Kruger national park: do buffalo play a role in the inter-epidemic circulation of virus?

Rift Valley fever (RVF) is a zoonotic mosquito-borne virus disease of livestock and wild ruminants that has been identified as a risk for international spread. Typically, the disease occurs in geographically limited outbreaks associated with high rainfall events and can cause massive losses of livestock. It is unclear how RVF virus persists during inter-epidemic periods but cryptic cycling of the virus in wildlife populations may play a role. We investigated the role that free-living African buffalo (Syncerus caffer caffer) might play in inter-epidemic circulation of the virus and looked for geographic, age and sex patterns of Rift Valley fever virus (RVFV) infection in African buffalo. Buffalo serum samples were collected (n = 1615) in Kruger National Park (KNP), South Africa, during a period of 1996-2007 and tested for antibodies to RVF. We found that older animals were more likely to be seropositive for anti-RVFV antibody than younger animals, but sex was not correlated with the likelihood of being anti-RVFV antibody positive. We also found geographic variation within KNP; herds in the south were more likely to have acquired anti-RVFV antibody than herds farther north - which could be driven by host or vector ecology. In all years of the study between 1996 and 2007, we found young buffalo (under 2 years of age) that were seropositive for anti-RVFV antibody, with prevalence ranging between 0 and 27% each year, indicating probable circulation. In addition, we also conducted a 4-year longitudinal study on 227 initially RVFV seronegative buffalo to look for evidence of seroconversion outside known RVF outbreaks within our study period (2008-2012). In the longitudinal study, we found five individuals that seroconverted from anti-RVFV antibody negative to anti-RVFV antibody positive, outside of any detected outbreak. Overall, our results provide evidence of long-term undetected circulation of RVFV in the buffalo population.

Encephalomyocarditis virus mortality in semi-wild bonobos (Pan panicus)

BACKGROUND

Fatal myocarditis from encephalomyocarditis virus (EMCV) infection has previously been identified in sporadic and epidemic forms in many species of captive non-human primates probably including one bonobo (Pan paniscus).

METHODS

We investigated the deaths of two bonobos that were suspicious of EMCV using a combination of histopathology, immunohistochemistry and, for one of the two bonobos, reverse transcription PCR.

RESULTS

Histopathological examination of heart tissue from the two bonobos showed changes characteristic of EMCV. Immunohistochemical studies confirmed the presence of EMCV antigen in heart tissue of both and in kidney and intestine of one of the bonobos. EMCV RNA was also isolated from the serum of the bonobo tested.

CONCLUSION

Together, these findings confirm that EMCV was responsible for deaths of the two bonobos. Strict separation of bonobos in particular and captive primates in general from potential sources of EMCV contamination should be maintained to prevent mortality caused by EMCV.

Epidemiology and pathogenicity of African bat lyssaviruses

Lyssaviruses belonging to all four known African Lyssavirus genotypes (gts) have been reported and isolated from SouthAfrica over the past few decades. These are: (1) Duvenhage virus (gt4), isolated again in 2006 from a human fatality; (2) Mokola virus (gt3), isolated irregularly, mostly from cats; (3) Lagos bat virus (gt2) continually isolated over the past four years from Epomophorus fruit bats and from incidental terrestrial animals and (4) Rabies virus (gt1) - with two virus biotypes endemic in mongoose and in canid species (mostly domestic dogs, jackals and bat-eared foxes), respectively. Only two of these are associated with bats in Southern Africa, viz. Duvenhage virus and Lagos bat virus (gts 4 and 2). For both these genotypes the authors have embarked on a programme of comparative study of molecular epidemiology. Duvenhage virus nucleoprotein nucleotide sequence analysis indicated a very low nucleotide diversity even though isolates were isolated decades apart. In contrast, individual isolates of Lagos bat virus were found to differ significantly with respectto nucleoprotein gene nucleotide sequence diversity as well as in pathogenicity profiles.

Molecular epidemiology of African and Asian Crimean-Congo haemorrhagic fever isolates

Phylogenetic relationships were examined for 70 Crimean-Congo haemorrhagic fever (CCHF) isolates from southern, central and West Africa, the Middle East and Greece using sequence data determined for a region of the S segment of the genome. Analysis revealed up to 18% genetic differences. Tree topology supports previous evidence for the existence of three groups of genetically related isolates, A, B and C. Within group A there are two clades: an African clade and a predominantly Asian clade comprising isolates from Pakistan, China, Iran, Russia and Madagascar. Group B includes isolates from southern and West Africa and Iran, and group C includes a single isolate from Greece. Despite the potential which exists for dispersal of the virus between Africa and Eurasia, it appears that circulation of the virus is largely compartmentalized within the two land masses, and the inference is that the geographic distribution of phylogenetic groups is related to the distribution and dispersal of tick vectors of the virus.

Indirect enzyme-linked immunosorbent assay for the detection of antibody against Rift Valley fever virus in domestic and wild ruminant sera

An indirect enzyme-linked immunosorbent assay (I-ELISA) for the detection of specific IgG immunoglobulins against Rift Valley fever virus (RVFV) was validated in-house. A total of 3055 sera from sheep (n = 1159), goats (n = 636), cattle (n = 203), African buffalo (n = 928), and other wild ruminants (n = 129), including eland, kudu, and black wildebeest, was used. Sera from domestic ruminants were collected in West (n = 10), South (n = 1654) and East Africa (n = 334), and sera from wild ruminants (n = 1064) were collected in South Africa. In addition, 136 sera from eight experimentally RVFV-infected sheep, taken during a period of 28 days post infection (dpi), were used to study the kinetics of RVFV antibody production. Field sera were tested by the serum neutralization (VN) test and experimental sera by VN and haemagglutination-inhibition (HI) test. Based on VN test results, negative sera were regarded as reference controls from RVFV-free, and positive sera were regarded as reference controls from RVFV-infected subpopulations of animals. ELISA data were expressed as the percentage positivity (PP) of an internal high positive control. The two-graph receiver operating characteristics approach was used for the selection and optimization of I-ELISA cut-offs including the misclassification costs term and Youden index (J). In addition, cut-off values were determined as the mean plus two-fold standard deviation of the result observed with the RVFV-free subpopulations. Established optimal cut-offs were different for each of the data sets analyzed, and ranged from 1.65 PP (buffalo) to 9.1 PP (goats). At the cut-off giving the highest estimate of combined measure of diagnostic accuracy (highest J value), the I-ELISA test parameters were determined as follows: (1) Diagnostic sensitivity (%): cattle--84.31, buffalo--94.44, sheep--98.91, goats--99.18. (2) Diagnostic specificity (%): cattle--99.34, buffalo--98.28, sheep--99.16, goats--99.23 and other game ruminants--99.26. In the group of RVFV-experimentally infected sheep, seroconversion In all individuals was detected by VN on 4-6 dpi, by HI on 5-7 dpi, and by I-ELISA on 6-7 dpi. All tests showed the same kinetic pattern of immunological response. Antibody levels were low for a very short period before increasing to high titres, after which it was easily detectable by all tests. Compared to traditional tests, the lower sensitivity of I-ELISA in the detection of the earliest stage of immunological response may be practically insignificant, particularily when this assay is used in population-based, disease-surveillance programmes. The high sensitivity and specificity of I-ELISA established in this study, especially for the statistically more representative subpopulations of animals tested, seem to support this prediction. Test parameters determined in this study should, however, be regarded as in-house diagnostic decision limits, for which further updating is recommended, particularly for specimens from other countries, and preferably by applying a standardized method for sampling of new subpopulations of animals to be targeted by the assay.

The 2000 epidemic of Rift Valley fever in Saudi Arabia: mosquito vector studies

In mid-September 2000, Rift Valley fever (RVF) virus was diagnosed as the cause of infection in humans and livestock in Jizan Region, Saudi Arabia. This is the first time that this arbovirus has been found outside Africa and Madagascar. Collections of mosquitoes (Diptera: Culicidae) were therefore undertaken (from 25 September to 10 October) at eight sites during the epidemic to obtain mosquitoes for attempted RVF virus isolation. Among 23 699 mosquito females tested, six isolations of RVF virus were made from 15 428 Culex (Culex) tritaeniorhynchus Giles and seven from 8091 Aedes (Aedimorphus) vexans arabiensis Patton [corrected]. Minimum mosquito infection rates per 1000 at sites with infected mosquitoes were 0.3-13.8 Cx. tritaeniorhynchus and 1.94-9.03 Ae. v. arabiensis. Viral activity moved northwards as collecting was in progress and collectors 'caught up' with the virus at the two most northerly sites on the last two trapping evenings. Other species occurred in small numbers and were identified but not tested. Both Cx. tritaeniorhynchus and Ae. v. arabiensis were susceptible to RVF virus and transmitted between hamsters, and an additional quantitative test with Cx. tritaeniorhynchus showed that 71-73% of mosquitoes became infected after ingesting 6.9-7.9 log10 FFU/mL of virus; transmission rates were 10% (post-infection day 14) and 26% (post-infection day 20). It was concluded that both species were vectors on grounds of abundance, distribution, preference for humans and sheep, the virus isolations and vector competence tests.

Experimental detection of Rift Valley fever virus by reverse transcription-polymerase chain reaction assay in large samples of mosquitoes

A reverse transcription-polymerase chain reaction (RT-PCR) was assessed in laboratory tests to detect the presence of single Aedes aegypti (L.) or Eretmapodites quinquevittatus Theobald mosquitoes infected with Rift Valley fever virus in pools of mosquitoes, 50-600 in size, from laboratory colonies or mixed field collections. The viral RNA was detected in all pools containing infected mosquitoes and was shown to be as sensitive as infant mice but more sensitive than Vero cell cultures for virus detection. Pools diluted down to the equivalent of 1:16 000 mosquitoes were also positive by RT-PCR. RNAs from 4 other phleboviruses were negative, there were no false positives and the procedure followed, with the 2 particular primers chosen, gave consistently clear bands of the PCR products on agarose gels without nested PCR being necessary.

Unexpected Ebola virus in a tertiary setting: clinical and epidemiologic aspects

OBJECTIVES

To describe the clinical manifestations of viral hemorrhagic fever, and to increase clinicians' awareness and knowledge of these illnesses.

DESIGN

Retrospective study of the clinical and laboratory data and management of two cases of Ebola virus infection with key epidemiologic data provided.

SETTING

Two tertiary care hospitals.

PATIENTS

Two adult patients, the index case and the source patient, both identified as having Ebola, one of whom originated in Gabon.

INTERVENTIONS

One patient was admitted to the intensive care unit. The other was managed in a general ward.

MEASUREMENT AND MAIN RESULTS

Clinical and laboratory data are reported. One patient, a healthcare worker who contracted this illness in the course of her work, died of refractory thrombocytopenia and an intracerebral bleed. The source patient survived. Despite a long period during which the diagnosis was obscure, none of the other 300 contacts contracted the illness.

CONCLUSIONS

Identification of high-risk patients and use of universal blood and body fluid precautions will considerably decrease the risk of nosocomial spread of viral hemorrhagic fevers.

Serologic survey among hospital and health center workers during the Ebola hemorrhagic fever outbreak in Kikwit, Democratic Republic of the Congo, 1995

From May to July 1995, a serologic and interview survey was conducted to describe Ebola hemorrhagic fever (EHF) among personnel working in 5 hospitals and 26 health care centers in and around Kikwit, Democratic Republic of the Congo. Job-specific attack rates estimated for Kikwit General Hospital, the epicenter of the EHF epidemic, were 31% for physicians, 11% for technicians/room attendants, 10% for nurses, and 4% for other workers. Among 402 workers who did not meet the EHF case definition, 12 had borderline positive antibody test results; subsequent specimens from 4 of these tested negative. Although an old infection with persistent Ebola antibody production or a recent atypical or asymptomatic infection cannot be ruled out, if they occur at all, they appear to be rare. This survey demonstrated that opportunities for transmission of Ebola virus to personnel in health facilities existed in Kikwit because blood and body fluid precautions were not being universally followed.

A novel immunohistochemical assay for the detection of Ebola virus in skin: implications for diagnosis, spread, and surveillance of Ebola hemorrhagic fever. Commission de Lutte contre les Epidémies à Kikwit

Laboratory diagnosis of Ebola hemorrhagic fever (EHF) is currently performed by virus isolation and serology and can be done only in a few high-containment laboratories worldwide. In 1995, during the EHF outbreak in the Democratic Republic of Congo, the possibility of using immunohistochemistry (IHC) testing of formalin-fixed postmortem skin specimens was investigated as an alternative diagnostic method for EHF. Fourteen of 19 cases of suspected EHF met the surveillance definition for EHF and were positive by IHC. IHC, serologic, and virus isolation results were concordant for all EHF and non-EHF cases. IHC and electron microscopic examination showed that endothelial cells, mononuclear phagocytes, and hepatocytes are main targets of infection, and IHC showed an association of cellular damage with viral infection. The finding of abundant viral antigens and particles in the skin of EHF patients suggests an epidemiologic role for contact transmission. IHC testing of formalin-fixed skin specimens is a safe, sensitive, and specific method for laboratory diagnosis of EHF and should be useful for EHF surveillance and prevention.

Markedly elevated levels of interferon (IFN)-gamma, IFN-alpha, interleukin (IL)-2, IL-10, and tumor necrosis factor-alpha associated with fatal Ebola virus infection

The role of immune mechanisms in the pathogenesis of Ebola hemorrhagic fever (EHF) remains to be elucidated. In this report, the serum cytokine levels of patients who died of EHF were compared with those of patients who recovered and those of control patients. A marked elevation of interferon (IFN)-gamma levels (>100 pg/mL) was observed in sequential serum samples from all fatal EHF cases compared with patients who recovered or controls. Markedly elevated serum levels of interleukin (IL)-2, IL-10, tumor necrosis factor (TNF)-alpha, and IFN-alpha were also noted in fatal EHF cases; however, they had a greater degree of variability. No differences were noted in serum levels of IL-4 and IL-6. mRNA quantitation from blood clots of the same patients showed relatively elevated levels of TNF-alpha and IFN-alpha in samples from EHF patients. Taken together, these results suggest that a high degree of immune activation accompanies and potentially contributes to a fatal outcome in EHF patients.

Clinical virology of Ebola hemorrhagic fever (EHF): virus, virus antigen, and IgG and IgM antibody findings among EHF patients in Kikwit, Democratic Republic of the Congo, 1995

Ebola hemorrhagic fever (EHF) patients treated at Kikwit General Hospital during the 1995 outbreak were tested for viral antigen, IgG and IgM antibody, and infectious virus. Viral antigen could be detected in virtually all patients during the acute phase of illness, while antibody was not always detectable before death. Virus was also isolated from patients during the course of their febrile illness, but attempts to quantify virus in Vero E6 cells by standard plaque assay were often unsuccessful. IgG and IgM antibody appeared at approximately the same time after disease onset (8-10 days), but IgM persisted for a much shorter period among the surviving convalescent patients. IgG antibody was detectable in surviving patients through about 2 years after onset, the latest time that samples were obtained. Detection of Ebola virus antigens or virus isolation appears to be the most reliable means of diagnosis for patients with suspected acute EHF, since patients with this often-fatal disease (80% mortality) may not develop detectable antibodies before death.

The reemergence of Ebola hemorrhagic fever, Democratic Republic of the Congo, 1995. Commission de Lutte contre les Epidémies à Kikwit

In May 1995, an international team characterized and contained an outbreak of Ebola hemorrhagic fever (EHF) in Kikwit, Democratic Republic of the Congo. Active surveillance was instituted using several methods, including house-to-house search, review of hospital and dispensary logs, interview of health care personnel, retrospective contact tracing, and direct follow-up of suspect cases. In the field, a clinical case was defined as fever and hemorrhagic signs, fever plus contact with a case-patient, or fever plus at least 3 of 10 symptoms. A total of 315 cases of EHF, with an 81% case fatality, were identified, excluding 10 clinical cases with negative laboratory results. The earliest documented case-patient had onset on 6 January, and the last case-patient died on 16 July. Eighty cases (25%) occurred among health care workers. Two individuals may have been the source of infection for >50 cases. The outbreak was terminated by the initiation of barrier-nursing techniques, health education efforts, and rapid identification of cases.

Experimental infection of ostriches with Crimean-Congo haemorrhagic fever virus

Following the occurrence of an outbreak of Crimean-Congo haemorrhagic fever (CCHF) among workers at an ostrich abattoir in South Africa in 1996, 9 susceptible young ostriches were infected subcutaneously with the virus in order to study the nature of the infection which they undergo. The ostriches developed viraemia which was demonstrable on days 1-4 following infection, with a maximum intensity of 4.0 log10 mouse intracerebral LD50/ml being recorded on day 2 in 1 of the birds. Virus was detectable in visceral organs such as spleen, liver and kidney up to day 5 post-inoculation, 1 day after it could no longer be found in blood. No infective virus was detected in samples of muscle, but viral nucleic acid was detected by reverse transcription-polymerase chain reaction in muscle from a bird sacrificed on day 3 following infection. It was concluded that the occurrence of infection in ostriches at abattoirs could be prevented by keeping the birds free of ticks for 14 days before slaughter.

The use of a reverse transcription-polymerase chain reaction for the detection of viral nucleic acid in the diagnosis of Crimean-Congo haemorrhagic fever

A reverse transcription-polymerase chain reaction (RT-PCR) was applied retrospectively to 80 stored serum samples from 45 confirmed Crimean-Congo haemorrhagic fever (CCHF) patients in southern Africa, and it was found that viral RNA could be detected in a proportion of samples up to day 16 of illness. Early in the disease there is relatively good correlation between the results obtained by RT-PCR and virus isolation, but after the first week it appears that infective virus is progressively cleared from serum while nucleic acid remains demonstrable in a proportion of patients well into convalescence. A further 47 serum samples from 38 patients with suspected viral haemorrhagic fever, 19 of whom proved to be cases of CCHF, were tested prospectively on being received at the laboratory. The combined use of RT-PCR with ethidium bromide stained gels for the detection of viral RNA, plus indirect immunofluorescence for the detection of IgG and IgM antibodies to CCHF virus, permitted a presumptive diagnosis to be reported within 8 h of receiving the first specimen from 18/19 cases of the disease studied prospectively. The nineteenth case was confirmed within 48 h when antibody response was demonstrated in a second serum sample. Viral nucleic acid was not detected in serum samples from 19 patients in whom alternative diagnoses were established.

Immunohistochemical and in situ localization of Crimean-Congo hemorrhagic fever (CCHF) virus in human tissues and implications for CCHF pathogenesis

BACKGROUND

Crimean-Congo hemorrhagic fever (CCHF) is a potentially fatal disease that occurs in parts of Africa, Asia, and eastern Europe, and that is caused by a recently emerged bunyavirus. Rapid laboratory diagnosis of CCHF infection is essential and is currently performed by virus isolation and serology. Histopathologic studies have been limited to a small number of cases, and little is known about the cellular tropism of CCHF virus and the pathogenesis of this disease.

DESIGN

We conducted a retrospective case analysis of 12 patients with a diagnosis of CCHF infection, confirmed by virus isolation, who were evaluated at the Special Pathogens Unit, National Institute for Virology, South Africa. The clinicopathologic features of CCHF and the diagnostic role of virus isolation as compared with serology, immunohistochemistry, and in situ hybridization were evaluated. Additionally, the distribution of CCHF virus in human tissues was examined.

RESULTS

The clinical and histopathologic features of CCHF resemble those of other viral hemorrhagic fevers. Of the 12 patients with virus isolation-confirmed CCHF infection, 5 were positive by serology, 10 by immunohistochemistry, and 5 by in situ hybridization. Immunohistochemistry and in situ hybridization analyses showed that the mononuclear phagocytes, endothelial cells, and hepatocytes are main targets of infection. Association of parenchymal necrosis in liver with viral infection suggests that cell damage may be mediated by a direct viral cytopathic effect.

CONCLUSIONS

The diagnosis of CCHF, suspected by history and clinical features, can be supported histopathologically. However, since the pathologic features resemble those of other viral hemorrhagic fevers, an unequivocal diagnosis can be made only by laboratory tests. The utility of immunohistochemistry as a sensitive and rapid diagnostic modality was established by the high degree of concordance with virus isolation. Infection of mononuclear phagocytes, endothelial cells, and hepatocytes may play a critical role in the pathogenesis of CCHF.

Isolation and phylogenetic characterization of Ebola viruses causing different outbreaks in Gabon

Three outbreaks of Ebola hemorrhagic fever have recently occurred in Gabon. Virus has been isolated from clinical materials from all three outbreaks, and nucleotide sequence analysis of the glycoprotein gene of the isolates and virus present in clinical samples has been carried out. These data indicate that each of the three outbreaks should be considered an independent emergence of a different Ebola virus of the Zaire subtype. As in earlier Ebola virus outbreaks, no genetic variability was detected between virus samples taken during an individual outbreak.

Investigation of tick-borne viruses as pathogens of humans in South Africa and evidence of Dugbe virus infection in a patient with prolonged thrombocytopenia

In the course of investigating suspected cases of viral haemorrhagic fever in South Africa patients were encountered who had been bitten by ticks, but who lacked evidence of infection with Crimean-Congo haemorrhagic fever (CCHF) virus or non-viral tick-borne agents. Cattle sera were tested by enzyme-linked immunoassay to determine whether tick-borne viruses other than CCHF occur in the country. The prevalence of antibody in cattle sera was 905/2116 (42.8%) for CCHF virus, 70/1358 (5.2%) for Dugbe, 21/1358 (1.5%) for louping ill, 6/450 (1.3%) for West Nile, 7/1358 (0.5%) for Nairobi sheep disease, 3/625 (0.5%) for Kadam and 2/450 (0.4%) for Chenuda. No reactions were recorded with Hazara, Bahig, Bhanja, Thogoto and Dhori viruses. The CCHF findings confirmed previous observations that the virus is widely prevalent within the distribution range of ticks of the genus Hyalomma, while antibody activity to Dugbe antigen was detected only within the distribution range of the tick Amblyomma hebraeum. Cross-reactivity for the nairoviruses, Hazara, Nairobi sheep disease and Dugbe, was detected in serum samples from 3/72 human patients with confirmed CCHF infection, and serum from 1/162 other patients reacted monospecifically with Dugbe antigen. The latter patient suffered from febrile illness with prolonged thrombocytopenia.

Experimental inoculation of plants and animals with Ebola virus

Thirty-three varieties of 24 species of plants and 19 species of vertebrates and invertebrates were experimentally inoculated with Ebola Zaire virus. Fruit and insectivorous bats supported replication and circulation of high titers of virus without necessarily becoming ill; deaths occurred only among bats that had not adapted to the diet fed in the laboratory.

Determining the refractive index and average thickness of AsSe semiconducting glass films from wavelength measurements only

The dispersive refractive index n(λ) and thickness d of chalcogenide glass thin films are usually calculated from measurements of both optical transmission and wavelength values. Many factors can influence the transmission values, leading to large errors in the values obtained for n(λ) and d. Anovel optical method is used to derive n(λ) and d for AsSe semiconducting glass thin films deposited by thermal evaporation in the spectral region where k(2) « n(2), using only wavelength values. This entails obtaining two transmission spectra: one at normal incidence and another at oblique incidence. The procedure yields values for the refractive index and average thickness of thermally evaporated chalcogenide films to an accuracy better than 3%.

An outbreak of encephalomyocarditis-virus infection in free-ranging African elephants in the Kruger National Park

A cluster of four deaths in late December 1993, marked the onset of an outbreak of disease of African elephants (Loxodonta africana) in the Kruger National Park (KNP) in South Africa, which has an estimated population of 7,500 elephants. Mortalities peaked in January 1994, with 32 deaths, and then declined steadily to reach pre-outbreak levels by September, but sporadic losses continued until November. During the outbreak altogether 64 elephants died, of which 53 (83%) were adult bulls. Archival records revealed that, in addition to the usual losses from known causes such as poaching and intraspecific fighting, sporadic deaths from unexplained causes had, in fact, occurred in widely scattered locations from at least 1987 onwards, and from that time until the perceived outbreak of disease there had been 48 such deaths involving 33 (69%) adult bulls. Carcases had frequently become decomposed or had been scavenged by the time they were found, but seven of eight elephants examined early in 1994 had lesions of cardiac failure suggestive of encephalomyocarditis (EMC)-virus infection, and the virus was isolated from the heart muscles of three fresh carcases. The results of tests for neutralizing antibody on 362 elephant sera collected for unrelated purposes from 1984 onwards and kept frozen, indicated that the virus had been present in the KNP since at least 1987. Antibody prevalences of 62 of 116 (53%) 18 of 139 (13%) and seven of 33 (21%) were found in elephants in three different regions of the KNP in 1993 and 1994. Studies had been conducted on myomorph rodents in the KNP for unrelated purposes since 1984, and trapping attempts were increased during the perceived outbreak of disease in elephants. There was a striking temporal correlation between the occurrence of a population explosion (as evidenced by markedly increased catch rates per trap-night) and a surge in prevalence of antibody to EM virus in rodents, and the occurrence of the outbreak of disease in elephants.

Serodiagnosis of Crimean-Congo haemorrhagic fever

Several methods for demonstrating antibody to Crimean-Congo haemorrhagic fever virus were compared on serum samples taken from 101 patients during the acute stage of illness and at intervals for up to 59 months thereafter, with emphasis on early detection of the immune response. The deaths of 23 patients on days 5-14 of illness were ascribed to the effects of the disease; two patients died later from other causes. Very few of the patients who died from the acute illness mounted an antibody response detectable by the methods tested. Four patients who died and 18 who recovered were treated with immune plasma collected from recovered patients. Treated patients acquired IgG antibody from the plasma, but it was possible to discern the onset of an endogenous IgM response in those individuals who survived the disease by all of the methods tested. Indirect immunofluorescence (IF) tests detected IgM and/or IgG antibodies at the earliest on day 4 of illness in about 10% of patients who survived the disease, and by day 9 all survivors had antibodies demonstrable by IF. A biotin-streptavidin IF technique offered no advantage over the standard IF test for the early detection of IgG antibody, but demonstrated higher antibody titres and detected IgM antibody earlier in about a quarter of the patients tested. An IgM-capture enzyme-linked immunoassay (ELISA) and an IgG sandwich ELISA demonstrated higher antibody titres than did IF tests, and detected antibody responses at an earlier stage of infection than did IF tests in about one-fifth of patients, but the reverse was true in a similar proportion of instances. A competition ELISA, which detected total antibody activity, produced lower titres than did the IgM and IgG ELISAs, but yielded results which were in close agreement with the findings in IF tests. It was concluded that the IF tests were most convenient for use in making a rapid serodiagnosis of the disease.

Enzyme-linked immunosorbent assays for the detection of antibody to Crimean-Congo haemorrhagic fever virus in the sera of livestock and wild vertebrates

IgM antibody response to Crimean-Congo haemorrhagic fever (CCHF) virus was monitored in experimentally infected sheep and cattle by an IgM capture enzyme-linked immunoassay (ELISA). Specific binding of antigen was detected by a rabbit anti-CCHF horseradish peroxidase conjugate or a sandwich technique with hyperimmune mouse anti-CCHF ascitic fluid and commercially available anti-mouse immunoglobulin peroxidase conjugate. The persistence of IgM antibody activity was found to be of shorter duration than in humans, and this may be a function of the relative lack of susceptibility of these animals to infection with CCHF virus. IgG antibody responses in the sheep could be monitored by sandwich ELISA using commercially available anti-sheep immunoglobulin peroxidase conjugates. Total antibody activity in the sera of experimentally infected sheep, cattle and small mammals could be monitored in a competitive ELISA (CELISA) using rabbit anti-CCHF peroxidase conjugate. The CELISA was applied to the sera of 960 wild vertebrates from a nature reserve in South Africa, and the prevalence of antibody was found to be greatest in large mammals such as rhinoceros, giraffe and buffalo, which are known to be the preferred hosts of the adult tick (Hyalomma) vectors of the virus.

Rabies in southern Africa

The first confirmed outbreak of rabies in Africa, believed to have followed the importation of an infected dog from England in 1892, occurred in the eastern Cape Province of South Africa, and was brought under control in 1894. An unconfirmed epidemic of rabies in dogs occurred in western Zambia in 1901. By the following year the disease had apparently spread along a major trade route, to cause an outbreak in Zimbabwe which engulfed most of the country before being eradicated in 1913. The existence of endemic rabies of viverrids (mongooses and genets) was confirmed in South Africa in 1928, and since then the viverrid disease has continued to occur widely on the interior plateau of the country with spill-over of infection to cattle and a variety of other animals. From about 1947 onwards, an invasive form of dog rabies spread from southern Zambia and/or Angola into Namibia, across northern and eastern Botswana into Zimbabwe and the northern Transvaal by 1950, entered Mozambique in 1952, and spread from there to Swaziland in 1954. Dog rabies extended from southern Mozambique into Natal in 1961 to cause a major epidemic which was brought under control in 1968. The disease re-entered northern Natal from Mozambique in 1976 and since then dog rabies has proved difficult to control in the peri-urban settlements of Natal-KwaZulu. The disease spread from Natal to Lesotho in 1982, and into the Transkei region of the eastern Cape Province in 1987, to reach the Ciskei by 1990. The spread of the disease in dogs was followed by the emergence of rabies of jackals and cattle in central Namibia, northern Botswana, Zimbabwe and the northern Transvaal. A unique outbreak of rabies in kudu antelope occurred in central Namibia from 1977 to 1985, apparently involving oral spread of infection between individuals. A few cases of rabies in the bat-eared fox were recognized each year in Namibia from 1967 onwards, and from the 1970s the occurrence of the disease in the fox has emerged as a distinct problem in the northern Cape Province and spread to the west coast. The rabies-related viruses, Lagos bat, Mokola and Duvenhage, associated with bats, shrews and rodents in Africa, are known to have caused isolated cases of disease in South Africa, and on one occasion a small outbreak involving six cats and a dog in Bulawayo, Zimbabwe.(ABSTRACT TRUNCATED AT 400 WORDS)

Risk of human infections with Crimean-Congo hemorrhagic fever virus in a South African rural community

Crimean-Congo hemorrhagic fever (CCHF) virus is widely distributed in wild and domestic mammals, birds, and ticks throughout many regions of Africa, Europe, and Asia. Interviews were conducted with 484 individuals from nine farms in the Republic of South Africa from which recent human CCHF cases had originated and with individuals from 27 farms without recognized cases. Serum samples were obtained from all consenting individuals. Blood was also drawn from 2,212 farm animals. Human infection with CCHF virus was uncommon (point prevalence 12.6/1,000). Antibody prevalence in humans on farms increased with age (P less than 0.001), and was correlated with handling lambs. Overall, a greater number of older animals were antibody positive than animals less than one year of age (P less than 0.001), but 12.7% of young animals on farms with human were antibody positive compared with 5.8% on those farms without human infection (P less than 0.05). Physical contact with ticks or tick bite was also found to be a risk factor, but contact with animal blood or fresh meat was not. The risk of CCHF virus infection in the community increased seven-fold following contact with a recognized CCHF case, even when other risk factors were taken into account (point prevalence rate 4.7%). In contrast, antibody prevalence was less than 1% (1 of 128) in the local hospital staff who had cared for patients with CCHF. Prevention is best achieved by education of the farming community and establishing and maintaining awareness in the hospital staff.

Encephalitis and chorioretinitis associated with neurotropic African horsesickness virus infection in laboratory workers. Part I. Clinical and neurological observations

Four laboratory workers from the same vaccine-packing facility developed at different times over an 8-year period an illness characterised by encephalitis (in 3 workers) and uveochorioretinitis (in 4). Low complement fixation titres were detected in all 4 patients to African horsesickness (AHS) virus and enzyme immunoassay and plaque reduction neutralising tests were positive, the latter against both serotypes 1 and 6. Five of 15 laboratory workers from the same facility who were healthy on clinical and ophthalmological examination showed positive plaque reduction neutralising tests but none to both serotypes 1 and 6. It is postulated that the encephalitis with the predominant temporal lobe involvement was caused by an airborne transnasal route of infection of the neurotropic AHS virus released in dried powder form, secondary to the accidental breaking of vaccine bottles. This is possibly the first report of subclinical and probable clinical neurotropic AHS infection in man.

Encephalitis and chorioretinitis associated with neurotropic African horsesickness virus infection in laboratory workers. Part III. Virological and serological investigations

Four cases of encephalitis with chorioretinitis occurred in the vaccine-packing section of a veterinary research institute: 1 in 1982, 1 in 1985 and 2 in 1989. No viruses were isolated from patients and serological tests failed to reveal significant antibodies to a range of viruses incorporated in veterinary vaccines or to other likely pathogens, except for low titres of complement-fixing antibody to African horsesickness (AHS) virus in all 4 patients. In confirmatory tests, high enzyme immunoassay titres of antibody to AHS virus occurred in the 4 patients and lower titres in 5/58 other workers at the institute. The 4 patients had significant plaque reduction neutralisation antibody titres to some of the strains of virus incorporated in AHS vaccine, particularly to serotypes 1 and 6, which had undergone neuro-adaptation through serial intracerebral passage in mice and which were known to be encephalitogenic following intranasal instillation in horses, guinea pigs and dogs. It is believed that the patients may have acquired aerosol infection with AHS virus as a result of accidental breakage of freeze-dried vaccine bottles.

Viraemic transmission of Crimean-Congo haemorrhagic fever virus to ticks

In order to determine the way in which vertebrates infected with Crimean-Congo haemorrhagic fever (CCHF) virus and potential ixodid tick vectors interact in nature, immature and adult ticks of several species were fed on viraemic mammals and then assayed for virus content at varying times after feeding. CCHF virus was not isolated from ticks of six species tested after feeding as adults and immature forms on sheep with viraemia of 10(2.5-3.2) LD 50/ml, nor from larval ticks fed on guinea-pigs and white-tailed rats with viraemia of 10(1.9-2.7) LD 50/ml. In contrast, virus was isolated from 10 of 152 pools of engorged adult ticks of 5 species that fed on cattle with viraemia of 10(1.5-2.7) LD 50/ml and from 3 of 137 female ticks after oviposition. Infection was transmitted to larval and nymphal Hyalomma truncatum and H. marginatum rufipes, but not to Rhipicephalus evertsi evertsi, from a scrub hare with viraemia of 10(4.2) LD 50/ml but only nymphal H. truncatum and H. m. rufipes became infected from scrub hares with viraemia of 10(2.6-2.7) LD 50/ml. Infection was transmitted trans-stadially in H. m. rufipes and H. truncatum infected as nymphae, and adult H. m. rufipes transmitted infection to a sheep. No evidence of transovarial transmission was found in larval progeny of ticks exposed to CCHF virus as adults on sheep and cattle or as immatures on scrub hares.

Teratogenicity of the Palyam serogroup orbiviruses in the embryonated chicken egg model

Embryonated chicken eggs were used as a model for assessing the teratogenic potential of several Palyam serogroup orbiviruses. Infection of 4-day-old embryonated chicken eggs via the yolk sac with eight of the viruses resulted in deaths or congenital deformities which included retarded development, arthrogryposis and reduced feathering. Statistical analysis showed that the viruses could be divided into three groups: those that caused death (Gweru virus isolates 866/77 and 1726/76; and Apies River virus), those that caused deaths only when large amounts of virus were inoculated (Gweru isolate AR11869 and Marondera virus) and those that caused death and deformities (Abadina, Kasba, Nyabira, Petevo and Vellore viruses). Differences in pathogenic potential were noted between isolates identified as the same serotype by serological tests.

Proteins of Palyam serogroup viruses

The replication and polypeptide synthesis of Abadina virus, a member of the Palyam serogroup of orbiviruses, was studied. The first virus-specified proteins could be demonstrated 2 to 4 h post-infection (p.i.) by immunoprecipitation. The rate of synthesis increased rapidly until 12 h p.i. after which it remained fairly constant until 18 h p.i. when it began to decline. Host cell protein synthesis shutoff was incomplete. Twelve virus-induced polypeptides were identified in infected cell lysates, ranging in Mr from 36K to 143K. Three small polypeptides (Mr 15K to 20K) identified in homologous immunoprecipitation studies are also thought to be virus-specified. Nine structural proteins were identified, four being major components of the purified virion. Partial proteolysis was used to demonstrate homology between some proteins. Pulse-chase experiments provided no evidence for a precursor-product relationship between any of the Abadina virus proteins. A non-structural protein was found to be phosphorylated.

The clinical pathology of Crimean-Congo hemorrhagic fever

Observations were made of 15 fatal and 35 nonfatal Crimean-Congo hemorrhagic fever (CCHF) infections diagnosed from February 1981 to March 1987 in Kimberly and Sandringham, Republic of South Africa. Following an incubation period of 2-9 days after exposure to infection, patients had a sudden onset of disease with fever, nausea, severe headache, and myalgia. Petechial rash and hemorrhagic signs such as epistaxis, hematemesis, and melena supervened on days 3-6 of illness. Deaths occurred on days 5-14 of illness. Patients with fatal infections had thrombocytopenia and markedly elevated levels of serum aspartate and alanine aminotransaminases, gamma-glutamyltransferase, lactic dehydrogenase, creatine kinase, bilirubin, creatinine, and urea. Total protein, albumin, fibrinogen, and hemoglobin levels were depressed. Values for prothrombin ratio, activated partial thromboplastin time, thrombin time, and fibrin degradation products were grossly elevated, findings that indicate the occurrence of disseminated intravascular coagulopathy. Many of the clinical pathologic changes were evident at an early stage of the disease and had a highly predictive value for fatal outcome of infection. Changes were present but less marked in nonfatal infections.

Antibody response in Crimean-Congo hemorrhagic fever

IgG and IgM antibodies became demonstrable by indirect immunofluorescence on days 7 to 9 of illness in 35 survivors of Crimean-Congo hemorrhagic fever. Maximum titers of antibody were usually attained in the second to third week of illness. Titers of IgM declined gradually thereafter and were low or negative by the fourth month. In some patients titers of IgG increased markedly between 2 and 4 months after onset of illness and remained readily demonstrable by indirect immunofluorescence 3 years after infection. Endogenous antibody response was demonstrated in only two of 15 patients who died of infection. Techniques for demonstrating antibody were (in order of decreasing sensitivity) enzyme-linked immunosorbent assay, reversed passive hemagglutination-inhibition, indirect immunofluorescence, fluorescent-focus reduction, complement-fixation, and immunodiffusion. Most patients developed relatively low levels of neutralizing antibodies (range, 1:8 to 1:32 by fluorescent-focus reduction tests), but some developed titers of 1:256 to 1:512. Plasma intended for therapeutic use should be selected on the basis of its neutralizing ability.

Viremia and antibody response of small African and laboratory animals to Crimean-Congo hemorrhagic fever virus infection

Eleven species of small African wild mammals, laboratory rabbits, guinea pigs, and Syrian hamsters were infected with Crimean-Congo hemorrhagic fever (CCHF) virus. Low-titered viremia followed by development of antibody was observed in scrub hares (Lepus saxatilis), Cape ground squirrels (Xerus inauris), red veld rats (Aethomys chrysophilus), white tailed rats (Mystromys albicaudatus), bushveld gerbils (Tatera leucogaster), striped mice (Rhabdomys pumilio), and guinea pigs. The maximum viremic titer in 4 scrub hares was 10(1.7-4.2) 50% mouse lethal doses/ml. Viremia was detected in 1/17 infected laboratory rabbits. Antibody response was only detected in South African hedgehogs (Atelerix frontalis), highveld gerbils (T. brantsii), Namaqua gerbils (Desmodillus auricularis), 2 species of multimammate mouse (Mastomys natalensis and M. coucha), and Syrian hamsters. The results of the study indicate that a proportion of infected scrub hares develop CCHF viremia of an intensity shown in the Soviet Union to be sufficient for infection of feeding immature ixodid ticks, but that South African hedgehogs and wild rodents are unlikely to be of importance as maintenance hosts of the virus in southern Africa.

Characterization of Palyam serogroup orbiviruses isolated in South Africa and serologic evidence for their widespread distribution in the country

The finding that there had been multiple isolations of Palyam serogroup orbiviruses from aborted cattle fetuses in neighbouring Zimbabwe, suggested that there was a need to investigate the possible occurrence of the viruses in South Africa. Unidentified viruses isolated in South Africa, which had been in storage, were examined. Four viruses which had been isolated from Culicoides midges collected at various sites in the years from 1969 to 1977, were identified as three strains of Gweru virus and one of the Nyabira virus (Palyam group serotypes originally described from Zimbabwe). A fifth virus, isolated in 1967 from the blood of a cow with mild fever, was found to be a distinct new member of the Vellore antigenic complex of the Palyam serogroup and was named Apies River virus. Sera from 476 cattle, 150 sheep, 24 goats and 78 humans from 10 farms were tested for neutralizing antibodies to the above three serotypes of virus plus Abadina and Marondera serotypes. Only 1 of 100 cattle sera from two farms in the southern coastal area had antibody, but elsewhere there was a high prevalence of antibody with 254 (53%) of all cattle exhibiting activity for one or more of the five serotypes of virus tested. Only 6 (4%) sheep, 3 (12.5%) goats and 11 (14%) humans had antibody.

Experimental studies on the replication and transmission of Crimean-Congo hemorrhagic fever virus in some African tick species

Seven African tick species were studied as potential vectors of Crimean-Congo hemorrhagic fever (CCHF) virus. Engorged nymphae of 4 ixodid species, Hyalomma marginatum rufipes, H. truncatum, Rhipicephalus evertsi mimeticus, and Amblyomma hebraeum, were inoculated intracoelomically with CCHF virus and assayed for virus content at varying times post-inoculation. The virus replicated in all 4 species, reaching maximum titers of 4.6-5.5(10) fluorescence focus units per ml on days 5-9 post-inoculation. Virus titers declined up to the molt, but increased slightly on emergence of adult ticks. Thereafter, virus titers declined progressively, but infectivity could still be detected in adult ticks for up to 205 days post-inoculation. Groups of H. m. rufipes, H. truncatum, and R.e. mimeticus infected adults were fed on susceptible sheep and successfully transmitted CCHF infection. CCHF virus was not isolated from pools of the larval and nymphal progeny of the female ticks nor did the larvae transmit infection to guinea pigs by bite. CCHF virus failed to replicate in adults and nymphae of 3 argasid tick species, Argas walkerae, Ornithodorus porcinus porcinus, and O. savignyi, after intracoelomic inoculation and could be reisolated from the ticks no later than 1 day post-inoculation. The results suggest that all ixodid ticks are capable of transmitting CCHF virus but argasid ticks do not appear to be capable of serving as vectors.

An outbreak of suspected water-borne epidemic non-A non-B hepatitis in northern Botswana with a high prevalence of hepatitis B carriers and hepatitis delta markers among patients

From June to December 1985 273 cases of hepatitis and jaundice were diagnosed in Maun, northern Botswana. It was known before the outbreak that most adults were immune to hepatitis A virus, most had markers indicating past infection with hepatitis B virus (HBV), there was a mean prevalence of 13.6% (57/418) HBsAg carriers, and a proportion of people had antibodies to hepatitis delta virus (HDV). There was evidence that faecal contamination of water supplies preceded the outbreak; the epidemic curve suggested that there was a major common source of infection; the disease appeared to have affected 1-2% of the population; 90.3% (214/237) patients for whom information is available were aged 20 years or older; the disease was generally mild and affected pregnant women most severely. 49 patients were admitted to hospital and at least 4/273 died. There were prevalences of 47% (28/60) HBsAg and 69% (37/54) anti-HDV reactors among patients bled 1-43 d after the onset of illness. The main features of the outbreak conformed to published descriptions of water-borne epidemic non-A non-B hepatitis and it is postulated that the disease was most severe in patients with active HBV infection and in those with HDV superinfection, so that such patients were disproportionately represented amongst those seeking medical attention.

Observations on antibody levels associated with active and passive immunity to African horse sickness

Tests for neutralising (NT) antibodies to the nine serotypes of African horse sickness (AHS) virus on the sera of three groups of horses confirmed that an increasing number of immunisations with vaccine containing attenuated strains of serotypes 1 to 6 of the virus, leads to broader response to the various serotypes and to higher individual titres. Nevertheless some horses failed to respond to one or more serotypes despite receiving numerous immunisations and it was clear that vaccine containing only serotypes 1 to 6 could not be relied upon to induce adequate cross-immunity to serotypes 7 to 9 of the virus. Highest antibody titres and broadest cross-reactivity were recorded in a fourth group of horses which had apparently suffered natural infection recently. The levels of antibody acquired from colostrum by seven foals generally correlated well with the levels of antibody in the sera of their dams and the rate of decline of passively acquired antibody was proportional to initial titre. Antibodies to individual serotypes of virus declined to undetectable levels in two to four months from birth in some instances implying that susceptibility to infection could occur well before the age of six to nine months which is commonly recommended for initial immunisation. Vaccination of eight foals at three to four months of age resulted in weak antibody response but did not adversely affect pre-existing low levels of maternal antibody so that early immunisation could be recommended as a means for attempting to control the losses of foals experienced in Zimbabwe.

Characterization of potentially foetotropic Palyam serogroup orbiviruses isolated in Zimbabwe

Twelve Palyam serogroup orbiviruses isolated in Zimbabwe from aborted cattle foetuses, plus one isolated from the visceral organs of a cow and another from vulture faeces, were examined in comparison with known members of the serogroup by complement fixation, indirect immunofluorescence, fluorescent focus reduction neutralization tests and PAGE of the segmented, dsRNA genomes. The viruses were indistinguishable from known members of the serogroup by complement fixation and indirect immunofluorescence, but two novel viruses, for which the names Gweru and Marondera are proposed, and two previously described viruses, Nyabira and Abadina, were identified by neutralization tests. The dsRNA profiles of Abadina serotype isolates differed from that of the Abadina prototype virus, indicating that different electropherotypes may occur within serotypes.