1. Regional Office for Public Health in Castilla y León, Spain
2. Epidemiology office in Palencia, Castilla y León, Spain
3. Epidemiology office in Zamora, Castilla y León, Spain
4. Epidemiology office in León, Castilla y León, Spain
5. Epidemiology office in Valladolid, Castilla y León, Spain
6. Epidemiology office in Burgos, Castilla y León, Spain
7. Epidemiology office in Salamanca, Castilla y León, Spain
In late June 2007, the Epidemiological Surveillance Network in Castilla y León, northern Spain, reported a series of cases in a rural area in the province of Palencia and in the provincial capital city of León, labelled as “fever of unknown origin”. Subsequent epidemiological investigation confirmed an outbreak of tularaemia.
On 22 October, the Epidemiological Surveillance Network in Castilla y León confirmed 362 cases of tularaemia, using the case definition and confirmation criteria agreed by the National Network for Epidemiological Surveillance together with the Epidemiological and Control Surveillance Network for Communicable Diseases in the European Union [1,2].
A clinical picture compatible with one of the different forms of tularaemia included:
Ulceroglandular (cutaneous ulcer with regional lymphadenopathy),
Glandular (regional lymphadenopathy with no ulcer),
Oculoglandular (conjunctivitis with preauricular lymphadenopathy),
Oropharyngeal (stomatitis or pharyngitis or tonsillitis and cervical lymphadenopathy),
Intestinal (intestinal pain, vomiting, and diarrhoea),
Pneumonic (primary pneumonic disease),
Typhoidal (febrile illness without early localising signs and symptoms).
Laboratory criteria for diagnosis:
Isolation of Francisella tularensis from a clinical specimen,
Detection of Francisella tularensis genome by PCR,
Demonstration of a specific antibody response in paired serum samples.
Case classification of confirmed case: a clinically compatible case that is confirmed by laboratory.
Cases were confirmed using serological techniques (microagglutination in 74.8% and tube agglutination in 25.2%), culture in 6% or PCR in 2%. F. tularensis holarctica has been identified as the causative agent of the outbreak.
The onset of symptoms in half of the cases occurred between epidemiological weeks 28 (ending 14 July) and 31 (ending 4 August); 81.4% of reported cases were males and 18.6% females. Some 62.5% of cases were concentrated in the 45 to 64 year-old age group, although all ages were affected (six to 88 years old).
The presentation of the disease in the cases analysed to date is shown in the table.
Some 74.6% of the cases were treated as out-patients by General Practitioners, while the rest required hospitalisation. Patient recovery in all cases was favourable, with a good response to the prescribed antibiotic treatment and few complications. The most frequently used antibiotics in this outbreak have been ciprofloxacin (750mg/12 hours, 10-14 days) and doxycycline (100 mg/12 hours, 10-14 days), but other fluroquinolones and tetracyclines were also used.
The epidemiological surveillance showed that 33.7% of cases were farm workers or people whose jobs involve contact with the environment (for example gardeners and lake and reservoir maintenance staff). A significant number of cases report having been in contact with rodents (23.5%), recent arthropod bites (16.6%) or animals such as dogs or cats (17.4%), or having handled crayfish (17.1%), taken frequent walks in the country (10.5%), having contact with livestock (9.7%), straw, manure or alfalfa hay (5.8%) or having handled and/or skinned hares (4.4%).
The most frequent clinical presentation of the disease and background risk factors reported suggest two different means of transmission responsible for the outbreak; firstly and principally by inhaling the bacteria, a pattern seen in just over half the cases (pneumonic and probably many of the typhoid forms); and secondly, through direct inoculation with local manifestations of the disease.
Further cases are actively being sought. The general public and, in particular, workers with high risk of exposure have been informed of the disease and of preventive measures that should be taken. These were:
- Avoid contact with dead, sick or unusually behaving animals,
- Avoid the consumption of unsanitary water that has not had adequate sanitary control,
- Use protective clothing and repellent products to avoid bites from insects and ticks,
- Use gloves and masks when handling animals,
- Do not allow children to touch dead animals,
- Ensure that the meat of wild animals is cooked through before you eat it. Freezing does not inactivate the agent responsible for tularaemia,
- Communicate to hunting and/or animal health authorities the presence of dead, sick or unusually behaving animals,
- In case of the appearance of symptoms compatible with this disease, contact your doctor immediately.
We believe that the exposure in this outbreak has come to an end. The majority of recently confirmed cases have an old onset of symptoms. The outbreak is focused in the central areas of Castilla y León (in five of nine provinces) and has not spread to all areas of Castilla y León, or to other Spanish regions. Taking this and the specific climatic and other conditions in the affected provinces into account, we believe that a spread of this outbreak to Portugal is unlikely.
Tularaemia has been identified as a potential agent for intentional release, but due to the fact that this outbreak occurred in a rural area that has fauna and crops with very particular characteristics, and which has also experienced previous outbreaks of tularaemia, we believe it is naturally occurring. The first tularaemia outbreak in this region occurred in 1997 [3,4,6], with 534 cases, and there was another in 2004 with 13 cases . Between 2000 and 2003, seven cases were reported in this region . In the 1997 outbreak, the mechanism of transmission was by contact, while this year inhalation has been more frequent. We are still investigating this outbreak, but believe that unusual climatic and environmental circumstances may have contributed to it, together with the significant diversity of reservoirs and sources of infection that have taken part in transmission (leporids, sheep, rodents, canids, haematophagus vectors). All these factors have probably aided the proliferation of Francisella tularensis, a bacterium that can survive for long periods in water, mud and animal carcasses. We intend to undertake further studies in order to advance the knowledge of the causes of this outbreak.