Jo E. B. Halliday

Risk Factors for the Presence of High-Level Shedders of Escherichia coli O157 on Scottish Farms

ABSTRACT Escherichia coli O157 infections are the cause of sporadic or epidemic cases of often bloody diarrhea that can progress to hemolytic uremic syndrome (HUS), a systematic microvascular syndrome with predominately renal and neurological complications. HUS is responsible for most deaths associated with E. coli O157 infection. From March 2002 to February 2004, approximately 13,000 fecal pat samples from 481 farms with finishing/store cattle throughout Scotland were examined for the presence of E. coli O157. A total of 441 fecal pats from 91 farms tested positive for E. coli O157. From the positive samples, a point estimate for high-level shedders was identified using mixture distribution analysis on counts of E. coli O157. Models were developed based on the confidence interval surrounding this point estimate (high-level shedder, greater than 103 or greater than 104 CFU g−1 feces). The mean prevalence on high-level-shedding farms was higher than that on low-level-shedding farms. The presence of a high-level shedder on a farm was found to be associated with a high proportion of low-level shedding, consistent with the possibility of a higher level of transmission. Analysis of risk factors associated with the presence of a high-level shedder on a farm suggested the importance of the pathogen and individual host rather than the farm environment. The proportion of high-level shedders of phage 21/28 was higher than expected by chance. Management-related risk factors that were identified included the type of cattle (female breeding cattle) and cattle stress (movement and weaning), as opposed to environmental factors, such as water supply and feed.

A framework for evaluating animals as sentinels for infectious disease surveillance

The dynamics of infectious diseases are highly variable. Host ranges, host responses to pathogens and the relationships between hosts are heterogeneous. Here, we argue that the use of animal sentinels has the potential to use this variation and enable the exploitation of a wide range of pathogen hosts for surveillance purposes. Animal sentinels may be used to address many surveillance questions, but they may currently be underused as a surveillance tool and there is a need for improved interdisciplinary collaboration and communication in order to fully explore the potential of animal sentinels. In different contexts, different animal hosts will themselves vary in their capacity to provide useful information. We describe a conceptual framework within which the characteristics of different host populations and their potential value as sentinels can be evaluated in a broad range of settings.

Bringing together emerging and endemic zoonoses surveillance: shared challenges and a common solution.

Early detection of disease outbreaks in human and animal populations is crucial to the effective surveillance of emerging infectious diseases. However, there are marked geographical disparities in capacity for early detection of outbreaks, which limit the effectiveness of global surveillance strategies. Linking surveillance approaches for emerging and neglected endemic zoonoses, with a renewed focus on existing disease problems in developing countries, has the potential to overcome several limitations and to achieve additional health benefits. Poor reporting is a major constraint to the surveillance of both emerging and endemic zoonoses, and several important barriers to reporting can be identified: (i) a lack of tangible benefits when reports are made; (ii) a lack of capacity to enforce regulations; (iii) poor communication among communities, institutions and sectors; and (iv) complexities of the international regulatory environment. Redirecting surveillance efforts to focus on endemic zoonoses in developing countries offers a pragmatic approach that overcomes some of these barriers and provides support in regions where surveillance capacity is currently weakest. In addition, this approach addresses immediate health and development problems, and provides an equitable and sustainable mechanism for building the culture of surveillance and the core capacities that are needed for all zoonotic pathogens, including emerging disease threats.

Rickettsia felis Infection in Febrile Patients, Western Kenya, 2007–2010

To determine previous exposure and incidence of rickettsial infections in western Kenya during 2007–2010, we conducted hospital-based surveillance. Antibodies against rickettsiae were detected in 57.4% of previously collected serum samples. In a 2008–2010 prospective study, Rickettsia felis DNA was 2.2× more likely to be detected in febrile than in afebrile persons.

Brucellosis in low-income and middle-income countries.

Purpose of review Human brucellosis is a neglected, underrecognized infection of widespread geographic distribution. It causes acute febrile illness and a potentially debilitating chronic infection in humans, and livestock infection has substantial socioeconomic impact. This review describes new information regarding the epidemiology of brucellosis in the developing world and advances in diagnosis and treatment. Recent findings The highest recorded incidence of human brucellosis occurs in the Middle East and Central Asia. Fever etiology studies demonstrate brucellosis as a cause of undifferentiated febrile illness in the developing world. Brucellosis is a rare cause of fever among returning travelers, but is more common among travelers returning from the Middle East and North Africa. Sensitive and specific rapid diagnostic tests appropriate for resource-limited settings have been validated. Randomized controlled trials demonstrate that optimal treatment for human brucellosis consists of doxycycline and an aminoglycoside. Decreasing the burden of human brucellosis requires control of animal brucellosis, but evidence to inform the design of control programs in the developing world is needed. Summary Brucellosis causes substantial morbidity in human and animal populations. While improvements in diagnostic options for resource-limited settings and stronger evidence for optimal therapy should enhance identification and treatment of human brucellosis, prevention of human disease through control in animals remains paramount.

Dynamics of a morbillivirus at the domestic -wildlife interface

Significance Morbilliviruses are a growing concern because of their ability to infect multiple species. The spill-over of canine distemper virus (CDV) from domestic dogs has been associated with severe declines in wild carnivores worldwide, and therefore mass dog vaccination has been suggested as a potential control strategy. Focusing on three decades of CDV exposure data in dogs and lions of the Serengeti, we show that cyclic infection dynamics in lions initially driven by dogs became more frequent and asynchronous, suggesting that the wider dog population and other wildlife species drive CDV dynamics. Hence, although widespread dog vaccination reduced the infection in dogs, transmission to lion populations still occurred, warranting further investigation into effective management options of CDV in this species-rich ecosystem. Morbilliviruses cause many diseases of medical and veterinary importance, and although some (e.g., measles and rinderpest) have been controlled successfully, others, such as canine distemper virus (CDV), are a growing concern. A propensity for host-switching has resulted in CDV emergence in new species, including endangered wildlife, posing challenges for controlling disease in multispecies communities. CDV is typically associated with domestic dogs, but little is known about its maintenance and transmission in species-rich areas or about the potential role of domestic dog vaccination as a means of reducing disease threats to wildlife. We address these questions by analyzing a long-term serological dataset of CDV in lions and domestic dogs from Tanzania’s Serengeti ecosystem. Using a Bayesian state–space model, we show that dynamics of CDV have changed considerably over the past three decades. Initially, peaks of CDV infection in dogs preceded those in lions, suggesting that spill-over from dogs was the main driver of infection in wildlife. However, despite dog-to-lion transmission dominating cross-species transmission models, infection peaks in lions became more frequent and asynchronous from those in dogs, suggesting that other wildlife species may play a role in a potentially complex maintenance community. Widespread mass vaccination of domestic dogs reduced the probability of infection in dogs and the size of outbreaks but did not prevent transmission to or peaks of infection in lions. This study demonstrates the complexity of CDV dynamics in natural ecosystems and the value of long-term, large-scale datasets for investigating transmission patterns and evaluating disease control strategies.

Serologic Surveillance of Anthrax in the Serengeti Ecosystem, Tanzania, 1996–2009

Bacillus anthracis, the bacterium that causes anthrax, is responsible for varying death rates among animal species. Difficulties in case detection, hazardous or inaccessible carcasses, and misdiagnosis hinder surveillance. Using case reports and a new serologic assay that enables multispecies comparisons, we examined exposure to and illness caused by B. anthracis in different species in the Serengeti ecosystem in Tanzania during 1996–2009 and the utility of serosurveillance. High seroprevalence among carnivores suggested regular nonfatal exposure. Seropositive wildebeest and buffalo showed that infection was not invariably fatal among herbivores, whereas absence of seropositivity in zebras and frequent detection of fatal cases indicated high susceptibility. Exposure patterns in dogs reflected known patterns of endemicity and provided new information about anthrax in the ecosystem, which indicated the potential of dogs as indicator species. Serosurveillance is a valuable tool for monitoring and detecting anthrax and may shed light on mechanisms responsible for species-specific variability in exposure, susceptibility, and mortality rates.

Coxiella burnetii in humans, domestic ruminants, and ticks in rural western Kenya.

We conducted serological surveys for Coxiella burnetii in archived sera from patients that visited a rural clinic in western Kenya from 2007 to 2008 and in cattle, sheep, and goats from the same area in 2009. We also conducted serological and polymerase chain reaction-based surveillance for the pathogen in 2009–2010, in human patients with acute lower respiratory illness, in ruminants following parturition, and in ticks collected from ruminants and domestic dogs. Antibodies against C. burnetii were detected in 30.9% (N = 246) of archived patient sera and in 28.3% (N = 463) of cattle, 32.0% (N = 378) of goats, and 18.2% (N = 159) of sheep surveyed. Four of 135 (3%) patients with acute lower respiratory illness showed seroconversion to C. burnetii. The pathogen was detected by polymerase chain reaction in specimens collected from three of six small ruminants that gave birth within the preceding 24 hours, and in five of 10 pools (50%) of Haemaphysalis leachi ticks collected from domestic dogs.

Epidemiology of Leptospirosis in Africa: A Systematic Review of a Neglected Zoonosis and a Paradigm for ‘One Health’ in Africa

Background Leptospirosis is an important but neglected bacterial zoonosis that has been largely overlooked in Africa. In this systematic review, we aimed to summarise and compare current knowledge of: (1) the geographic distribution, prevalence, incidence and diversity of acute human leptospirosis in Africa; and (2) the geographic distribution, host range, prevalence and diversity of Leptospira spp. infection in animal hosts in Africa. Methods Following Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines, we searched for studies that described (1) acute human leptospirosis and (2) pathogenic Leptospira spp. infection in animals. We performed a literature search using eight international and regional databases for English and non-English articles published between January 1930 to October 2014 that met out pre-defined inclusion criteria and strict case definitions. Results and Discussion We identified 97 studies that described acute human leptospirosis (n = 46) or animal Leptospira infection (n = 51) in 26 African countries. The prevalence of acute human leptospirosis ranged from 2 3% to 19 8% (n = 11) in hospital patients with febrile illness. Incidence estimates were largely restricted to the Indian Ocean islands (3 to 101 cases per 100,000 per year (n = 6)). Data from Tanzania indicate that human disease incidence is also high in mainland Africa (75 to 102 cases per 100,000 per year). Three major species (Leptospira borgpetersenii, L. interrogans and L. kirschneri) are predominant in reports from Africa and isolates from a diverse range of serogroups have been reported in human and animal infections. Cattle appear to be important hosts of a large number of Leptospira serogroups in Africa, but few data are available to allow comparison of Leptospira infection in linked human and animal populations. We advocate a ‘One Health’ approach to promote multidisciplinary research efforts to improve understanding of the animal to human transmission of leptospirosis on the African continent.

Urban leptospirosis in Africa: a cross-sectional survey of Leptospira infection in rodents in the Kibera urban settlement, Nairobi, Kenya.

Leptospirosis is a widespread but under-reported cause of morbidity and mortality. Global re-emergence of leptospirosis has been associated with the growth of informal urban settlements in which rodents are thought to be important reservoir hosts. Understanding the multi-host epidemiology of leptospirosis is essential to control and prevent disease. A cross-sectional survey of rodents in the Kibera settlement in Nairobi, Kenya was conducted in September–October 2008 to demonstrate the presence of pathogenic leptospires. A real-time quantitative polymerase chain reaction showed that 41 (18.3%) of 224 rodents carried pathogenic leptospires in their kidneys, and sequence data identified Leptospira interrogans and L. kirschneri in this population. Rodents of the genus Mus (37 of 185) were significantly more likely to be positive than those of the genus Rattus (4 of 39; odds ratio = 15.03). Questionnaire data showed frequent contact between humans and rodents in Kibera. This study emphasizes the need to quantify the public health impacts of this neglected disease at this and other urban sites in Africa.