Outbreak of tularaemia connected to a contaminated well in the Västra Götaland region in Sweden

Tularemia From Veterinary Occupational Exposure

Tularemia is a disease caused by Francisella tularensis, a highly infectious bacteria that can be transmitted to humans by direct contact with infected animals. Because of the potential for zoonotic transmission of F. tularensis, veterinary occupational risk is a concern. Here, we report on a human case of tularemia in a veterinarian after an accidental needlestick injury during abscess drainage in a sick dog. The veterinarian developed ulceroglandular tularemia requiring hospitalization but fully recovered after abscess drainage and a course of effective antibiotics. To systematically assess veterinary occupational transmission risk of F. tularensis, we conducted a survey of veterinary clinical staff after occupational exposure to animals with confirmed tularemia. We defined a high-risk exposure as direct contact to the infected animal's body fluids or potential aerosol inhalation without use of standard personal protective equipment (PPE). Survey data included information on 20 veterinary occupational exposures to animals with F. tularensis in 4 states. Veterinarians were the clinical staff most often exposed (40%), followed by veterinarian technicians and assistants (30% and 20%, respectively). Exposures to infected cats were most common (80%). Standard PPE was not used during 80% of exposures; a total of 7 exposures were categorized as high risk. Transmission of F. tularensis in the veterinary clinical setting is possible but overall risk is likely low. Veterinary clinical staff should use standard PPE and employ environmental precautions when handling sick animals to minimize risk of tularemia and other zoonotic infections; postexposure prophylaxis should be considered after high-risk exposures to animals with suspected or confirmed F. tularensis infection to prevent tularemia.

Tularemia as a waterborne disease: a review

Francisella tularensis is a Gram-negative, intracellular bacterium causing the zoonosis tularemia. This highly infectious microorganism is considered a potential biological threat agent. Humans are usually infected through direct contact with the animal reservoir and tick bites. However, tularemia cases also occur after contact with a contaminated hydro-telluric environment. Water-borne tularemia outbreaks and sporadic cases have occurred worldwide in the last decades, with specific clinical and epidemiological traits. These infections represent a major public health and military challenge. Human contaminations have occurred through consumption or use of F. tularensis-contaminated water, and various aquatic activities such as swimming, canyoning and fishing. In addition, in Sweden and Finland, mosquitoes are primary vectors of tularemia due to infection of mosquito larvae in contaminated aquatic environments. The mechanisms of F. tularensis survival in water may include the formation of biofilms, interactions with free-living amoebae, and the transition to a 'viable but nonculturable' state, but the relative contribution of these possible mechanisms remains unknown. Many new aquatic species of Francisella have been characterized in recent years. F. tularensis likely shares with these species an ability of long-term survival in the aquatic environment, which has to be considered in terms of tularemia surveillance and control.

Tularemia transmission to humans: a multifaceted surveillance approach

Tularemia has sustained seroprevalence in Eurasia, with estimates as high as 15% in endemic regions. The purpose of this report is to characterise the current epidemiology of Francisella tularensis subspecies holarctica in Georgia. Three surveillance activities are summarised: (1) acute infections captured in Georgia's notifiable disease surveillance system, (2) infectious disease seroprevalence study of military volunteers, and (3) a study of seroprevalence and risk factors in endemic regions. Descriptive analyses of demographic, exposure and clinical factors were conducted for the surveillance studies; bivariate analyses were computed to identify risk factors of seropositivity using likelihood ratio χ2 tests or Fisher's exact tests. Of the 19 incident cases reported between 2014 and August 2017, 10 were confirmed and nine met the presumptive definition; the estimated annual incidence was 0.12/100 000. The first cases of tularemia in Western Georgia were reported. Seroprevalences of antibodies for F. tularensis were 2.0% for military volunteers and 5.0% for residents in endemic regions. Exposures correlated with seropositivity included work with hay and contact with multiple types of animals. Seroprevalence studies conducted periodically may enhance our understanding of tularemia in countries with dramatically underestimated incidence rates.

Environmental Surveillance of Zoonotic Francisella tularensis in the Netherlands

Tularemia is an emerging zoonosis caused by the Gram-negative bacterium Francisella tularensis, which is able to infect a range of animal species and humans. Human infections occur through contact with animals, ingestion of food, insect bites or exposure to aerosols or water, and may lead to serious disease. F. tularensis may persist in aquatic reservoirs. In the Netherland, no human tularemia cases were notified for over 60 years until in 2011 an endemic patient was diagnosed, followed by 17 cases in the 6 years since. The re-emergence of tularemia could be caused by changes in reservoirs or transmission routes. We performed environmental surveillance of F. tularensis in surface waters in the Netherlands by using two approaches. Firstly, 339 samples were obtained from routine monitoring -not related to tularemia- at 127 locations that were visited between 1 and 8 times in 2015 and 2016. Secondly, sampling efforts were performed after reported tularemia cases (n = 8) among hares or humans in the period 2013–2017. F. tularensis DNA was detected at 17% of randomly selected surface water locations from different parts of the country. At most of these positive locations, DNA was not detected at each time point and levels were very low, but at two locations contamination was clearly higher. From 7 out of the 8 investigated tularemia cases, F. tularensis DNA was detected in at least one surface water sample collected after the case. By using a protocol tailored for amplification of low amounts of environmental DNA, 10 gene targets were sequenced. Presence of F. tularensis subspecies holarctica was confirmed in 4 samples, and in 2 of these, clades B.12 and B.6 were identified. This study shows that for tularemia, information regarding the spatial and temporal distribution of its causative agent could be derived from environmental surveillance of surface waters. Tracking a particular strain in the environment as source of infection is feasible and could be substantiated by genotyping, which was achieved in water samples with only low levels of F. tularemia present. These techniques allow the establishment of a link between tularemia cases and environmental samples without the need for cultivation.