Kathleen A. Alexander

Novel Mycobacterium tuberculosis Complex Pathogen, M. mungi

Seven outbreaks involving increasing numbers of banded mongoose troops and high death rates have been documented. We identified a Mycobacterium tuberculosis complex pathogen, M. mungi sp. nov., as the causative agent among banded mongooses that live near humans in Chobe District, Botswana. Host spectrum and transmission dynamics remain unknown.

AFRICAN WILD DOGS (LYCAON PICTUS) ENDANGERED BY A CANINE DISTEMPER EPIZOOTIC AMONG DOMESTIC DOGS NEAR THE MASAI MARA NATIONAL RESERVE, KENYA

A longitudinal study of canine distemper (CD) among domestic dogs on Maasai communal land to the north of the Masai Mara National Reserve in Kenya was conducted from 1989 to 1991. Prevalence of antibodies to CD was very low among domestic dogs in 1989 and 1990 (4%, n = 49; and 1%, n = 119, respectively) and no African wild dogs (Lycaon pictus; n = 16) collected simultaneously from the same area had detectable antibodies. Among 51 domestic dogs sampled in 1991, however, prevalence of CD antibodies rose significantly (P < 0.01) to 76%. Disease-related mortality rates among domestic dogs were estimated from 1990 to 1992; they rose significantly (P < 0.01) from 21% in 1990 to 50% in 1991 and then decreased significantly (P < 0.01) to 38% in 1992. The 1992 mortality rate remained significantly (P < 0.01) higher than that of 1990. Signs observed in clinically ill domestic dogs were consistent with CD and included listlessness, decreased appetite, bilateral serous to mucopurulent oculonasal discharge, and diarrhea. No carcasses could be retrieved for virus isolation and postmortem examination. Concurrent with this CD epizootic in domestic dogs, the known African wild dog packs in this region disappeared.

Mycobacterium tuberculosis: An Emerging Disease of Free-Ranging Wildlife

Expansion of ecotourism-based industries, changes in land-use practices, and escalating competition for resources have increased contact between free-ranging wildlife and humans. Although human presence in wildlife areas may provide an important economic benefit through ecotourism, exposure to human pathogens may represent a health risk for wildlife. This report is the first to document introduction of a primary human pathogen into free-ranging wildlife. We describe outbreaks of Mycobacterium tuberculosis, a human pathogen, in free-ranging banded mongooses (Mungos mungo) in Botswana and suricates (Suricata suricatta) in South Africa. Wildlife managers and scientists must address the potential threat that humans pose to the health of free-ranging wildlife.

What Factors Might Have Led to the Emergence of Ebola in West Africa

An Ebola outbreak of unprecedented scope emerged in West Africa in December 2013 and presently continues unabated in the countries of Guinea, Sierra Leone, and Liberia. Ebola is not new to Africa, and outbreaks have been confirmed as far back as 1976. The current West African Ebola outbreak is the largest ever recorded and differs dramatically from prior outbreaks in its duration, number of people affected, and geographic extent. The emergence of this deadly disease in West Africa invites many questions, foremost among these: why now, and why in West Africa? Here, we review the sociological, ecological, and environmental drivers that might have influenced the emergence of Ebola in this region of Africa and its spread throughout the region. Containment of the West African Ebola outbreak is the most pressing, immediate need. A comprehensive assessment of the drivers of Ebola emergence and sustained human-to-human transmission is also needed in order to prepare other countries for importation or emergence of this disease. Such assessment includes identification of country-level protocols and interagency policies for outbreak detection and rapid response, increased understanding of cultural and traditional risk factors within and between nations, delivery of culturally embedded public health education, and regional coordination and collaboration, particularly with governments and health ministries throughout Africa. Public health education is also urgently needed in countries outside of Africa in order to ensure that risk is properly understood and public concerns do not escalate unnecessarily. To prevent future outbreaks, coordinated, multiscale, early warning systems should be developed that make full use of these integrated assessments, partner with local communities in high-risk areas, and provide clearly defined response recommendations specific to the needs of each community.

Rabies and African wild dogs in Kenya

Three packs of African wild dogs (Lycaon pictus) ranging to the north of the Masai Mara National Reserve in southwestern Kenya were monitored from 1988 to 1990. During a six week period (August 2–September 14, 1989), 21 of 23 members of one of these packs died. Histological examination of two brain samples revealed eosinophilic intracytoplasmic inclusions (Negri bodies), supporting a diagnosis of rabies viral encephalitis. An additional brain sample tested positive for rabies with a fluorescent antibody test. Nucleotide sequence of the rabies viral N and G genes from isolates of four African wild dogs (including an individual from Tanzania) indicated that infection was with a viral variant common among domestic dogs in Kenya and Tanzania. A hypothesis linking African wild dog rabies deaths to researcher handling is evaluated and considered implausible.

Serologic survey of selected canine pathogens among free-ranging jackals in Kenya

Serum samples from 76 free-ranging adult jackals of three species from four localities in Kenya were examined for circulating antibodies against four canine pathogens: rabies virus, canine parvovirus (CPV-2), canine distemper virus (CDV), and Ehrlichia canis. Samples were collected between April 1987 and January 1988. Among black-backed jackals (Canis mesomelas), the most sampled species, the mean prevalence of antibodies to CPV-2, CDV, rabies virus, and E. canis was 34% (14 positive/55 sampled), 9% (4/55), 3% (1/28), and 2% (1/36), respectively. There were no significant differences among sampling locations. In one area, antibody prevalence of CPV-2 was significantly higher for golden jackals (C. aureus; 9/16) than for C. mesomelas (5/26). Only three side-striped jackals (C. adustus) were sampled, but antibodies to CPV-2 and CDV were present. As jackals often are the most abundant wild carnivore in African ecosystems, they could serve as an important indicator species to monitor the potential of exposure of rare and endangered canids to specific canine diseases.

Climate Change is Likely to Worsen the Public Health Threat of Diarrheal Disease in Botswana

Diarrheal disease is an important health challenge, accounting for the majority of childhood deaths globally. Climate change is expected to increase the global burden of diarrheal disease but little is known regarding climate drivers, particularly in Africa. Using health data from Botswana spanning a 30-year period (1974–2003), we evaluated monthly reports of diarrheal disease among patients presenting to Botswana health facilities and compared this to climatic variables. Diarrheal case incidence presents with a bimodal cyclical pattern with peaks in March (ANOVA p < 0.001) and October (ANOVA p < 0.001) in the wet and dry season, respectively. There is a strong positive autocorrelation (p < 0.001) in the number of reported diarrhea cases at the one-month lag level. Climatic variables (rainfall, minimum temperature, and vapor pressure) predicted seasonal diarrheal with a one-month lag in variables (p < 0.001). Diarrheal case incidence was highest in the dry season after accounting for other variables, exhibiting on average a 20% increase over the yearly mean (p < 0.001). Our analysis suggests that forecasted climate change increases in temperature and decreases in precipitation may increase dry season diarrheal disease incidence with hot, dry conditions starting earlier and lasting longer. Diarrheal disease incidence in the wet season is likely to decline. Our results identify significant health-climate interactions, highlighting the need for an escalated public health focus on controlling diarrheal disease in Botswana. Study findings have application to other arid countries in Africa where diarrheal disease is a persistent public health problem.

Pathological manifestations of feline immunodeficiency virus (FIV) infection in wild African lions

Abstract Feline immunodeficiency virus (FIV) causes AIDS in the domestic cat (Felis catus) but has not been explicitly associated with AIDS pathology in any of the eight free-ranging species of Felidae that are endemic with circulating FIV strains. African lion (Panthera leo) populations are infected with lion-specific FIV strains (FIVple), yet there remains uncertainty about the degree to which FIV infection impacts their health. Reported CD4+ T-lymphocyte depletion in FIVple-infected lions and anecdotal reports of lion morbidity associated with FIV seroprevalence emphasize the concern as to whether FIVple is innocuous or pathogenic. Here we monitored clinical, biochemical, histological and serological parameters among FIVple-positive (N =47) as compared to FIVple-negative (N =17) lions anesthetized and sampled on multiple occasions between 1999 and 2006 in Botswana. Relative to uninfected lions, FIVple-infected lions displayed a significant elevation in the prevalence of AIDS-defining conditions: lymphadenopathy, gingivitis, tongue papillomas, dehydration, and poor coat condition, as well as displaying abnormal red blood cell parameters, depressed serum albumin, and elevated liver enzymes and gamma globulin. Spleen and lymph node biopsies from free-ranging FIVple-infected lions (N =9) revealed evidence of lymphoid depletion, the hallmark pathology documented in immunodeficiency virus infections of humans (HIV-1), macaques, and domestic cats. We conclude that over time FIVple infections in free-ranging lions can lead to adverse clinical, immunological, and pathological outcomes in some individuals that parallel sequelae caused by lentivirus infection in humans (HIV), Asian macaques (SIV) and domestic cats (FIVfca).

Multi-host pathogens and carnivore management in southern Africa

Abstract A retrospective serosurvey of multi-host feline and canine viruses among carnivore species in southern Africa (n =1018) identified widespread pathogen exposure even in remote protected areas. In contrast to mortality experienced in East African predators, canine distemper virus (CDV) infection among African wild dogs (Lycaon pictus) in Botswana was not associated with identifiable change in pup survivorship or disease related mortality of adults. A disease outbreak of unknown aetiology occurred in the same population over 4 weeks in 1996. Outbreak boundaries coincided with ecotones, not the spatial distribution of contiguous packs, highlighting the potential importance of landscape heterogeneities in these processes. Direct management of pathogens in domestic animal reservoirs is complicated by the apparent complexity of pathogen maintenance and transmission in these large systems. Conservation effort should be focused at securing large metapopulations able to compensate for expected episodic generalist pathogen invasion and attention directed to addressing underlying causes of population depression such as habitat loss and wildlife conflict.

Modeling of Wildlife-Associated Zoonoses: Applications and Caveats

Wildlife species are identified as an important source of emerging zoonotic disease. Accordingly, public health programs have attempted to expand in scope to include a greater focus on wildlife and its role in zoonotic disease outbreaks. Zoonotic disease transmission dynamics involving wildlife are complex and nonlinear, presenting a number of challenges. First, empirical characterization of wildlife host species and pathogen systems are often lacking, and insight into one system may have little application to another involving the same host species and pathogen. Pathogen transmission characterization is difficult due to the changing nature of population size and density associated with wildlife hosts. Infectious disease itself may influence wildlife population demographics through compensatory responses that may evolve, such as decreased age to reproduction. Furthermore, wildlife reservoir dynamics can be complex, involving various host species and populations that may vary in their contribution to pathogen transmission and persistence over space and time. Mathematical models can provide an important tool to engage these complex systems, and there is an urgent need for increased computational focus on the coupled dynamics that underlie pathogen spillover at the human-wildlife interface. Often, however, scientists conducting empirical studies on emerging zoonotic disease do not have the necessary skill base to choose, develop, and apply models to evaluate these complex systems. How do modeling frameworks differ and what considerations are important when applying modeling tools to the study of zoonotic disease? Using zoonotic disease examples, we provide an overview of several common approaches and general considerations important in the modeling of wildlife-associated zoonoses.