6.3.7. Other diseases of zoonotic and environmental origin

 

6.3.7.1. Summary

 

This is a very heterogeneous group of diseases that fall into two broad categories:

·          Diseases present in Europe (tularaemia, puumala virus infection, borreliosis, tick-borne encephalitis, Q fever, leptospirosis, anthrax, rabies, and West Nile virus infection). Some of these diseases have the potential to be used as a bioterrorism threat (anthrax and tularemia). At present, these diseases have a low number of cases, are often geographically confined, and have to be seen in relation to certain animal reservoirs. Surveillance has not been established for all of them in all countries. For each of these diseases there is a need to develop tailored monitoring, establish surveillance of outbreaks, monitor risk factors and standardise laboratory methods.

·          Diseases imported into Europe (malaria, viral haemorrhagic fevers (VHF), and plague). For these diseases it is important to have sufficient laboratory capacity for rapid diagnoses in travellers returning from endemic countries.

 

The most important of the above diseases are tularaemia, puumala virus infections, borreliosis and tick-borne encephalitis (TBE). Of these, only tularaemia is under EU surveillance. This is a disease mainly seen in the North and in sparsely populated areas of central Europe. It appears in outbreaks at intervals of several years, and any actual trend is difficult to describe. Puumala virus infection (nephropathia epidemica) could be classified as VHF, but is seldom reported as such in the EU.

 

A number of exotic diseases, such as VHF, malaria and plague should be reported to the EU network, but these cases are almost all imported. The main reason for surveillance of malaria is not to discover any transmission in the EU, but rather to ensure that recommendations for prophylaxis remain valid. Few of these diseases actually pose any major public health threat to EU citizens. Some of these diseases are prone to outbreaks, which always attract a great deal of media attention. It is important to follow their epidemiology in order to give adequate information to the EU public.

 

Environmental, ecological and climate changes contribute to the emergence, maintenance and transmission of vector-borne and other infectious diseases, some of them imported from regions where they are endemic. The effect of global warming on Europe in the years ahead could increase this danger.

This is a wide range of diseases with different modes of transmission and with varying relevance to European public health. More systematic surveillance data are needed in order to allow for a more coordinated approach in terms of prevention and control. Imported cases through travel need to be monitored, in particular where there is the potential for autochthonous transmission (malaria, chikungunya, yellow fever, etc.), high infectivity (most VHF), etc. Considering the type of diseases and their possible impact, we need to be able to ensure rapid diagnoses for each of them, as well as for unknown pathogens.

 

6.3.7.2. Diseases present in Europe

 

Tularemia

 

Tularaemia is a zoonosis, caused by the bacteria Francisella tularensis. Natural reservoirs include wild rabbits, hares and muskrats, as well as some domestic animals. Human infection occurs through a variety of mechanisms such as 1) bites from infected ticks; 2) direct contact or ingestion of water, food, or soil contaminated by rodents; 3) handling animal tissues or fluids or undercooked infected meat; and 4) inhalation of infective aerosols. Human-to-human transmission has not been documented. A vaccine is available to protect laboratory personnel routinely working with the bacterium. The pathogen has been considered as an agent with the potential for intentional release.

 

In the last 10 years the reported number of cases in the EU has been very variable, but the overall trend appears to be stable. Finland and Sweden were the countries reporting the most cases over the last 10 years and trends for both countries appear to be increasing, although more in Sweden. In 2005, 508 cases were reported by 21 countries. Sweden (2.73 per 100 000), followed by Hungary (0.86 per 100 000) reported the highest incidence rates.

 

 

Puumala haemorrhagic fever with renal syndrome

 

Puumala haemorrhagic fever with renal syndrome, also called ‘nephropathia epidemica’, is caused by the puumala virus, and occurs mainly in Northern Europe and Russia. Transmission to humans occurs through the inhalation of the virus in aerosols contaminated with the excreta of infected rodents. Up to 80% of infections may be asymptomatic. Clinical illness results in haemorrhagic fever with renal syndrome, with a death rate of less than 0.5%. This disease is the most common haemorrhagic fever in Europe. In the past 10 years, there has been an increase of cases every third year. The year 2005 saw one of these peaks, with more than 2 500 cases reported by Finland and 330 from Sweden. Higher than usual incidences were also noticed in France, Germany, Belgium, Austria, and Luxembourg.

 

Q fever

 

Q fever is a zoonosis caused by Coxiella burnetii, characterised by an acute febrile illness. The natural reservoirs are sheep, cattle, goats, cats, dogs, birds and some wild animals. Humans are usually infected by direct inhalation of aerosols during parturition of infected animals, or from the dust of contaminated premises. European-level surveillance data are incomplete, but in the last 10 years the overall trend appears to be rather stable with the rate varying between 0.2 and 0.5 cases per 100 000. In 2005, 958 cases were reported by 21 countries. Germany and France reported the highest incidence rates (0.49 per 100 000 and 0.48 per 100 000, respectively). This is a typically under-reported disease due to its unspecific clinical features.

 

 

Leptospirosis

 

Leptospirosis is a zoonotic disease with a wide clinical spectrum, caused by Leptospira bacteria. The death rate is low, but increases with advancing age and may reach 20% or more. Humans acquire the disease by occupational or recreational contact with water, soil or other material contaminated with the urine of infected animals. Infection in humans may follow direct or indirect exposure to an infected animal’s urine or contaminated fresh water.

 

The overall incidence was stable in the EU during the period 1995–2004, ranging from 0.1 to 0.22 cases per 100 000. The lowest number of cases in recent years (687) was reported in 2004. France continues to report a high number of cases, partly related to higher incidence in its overseas departments. In 2005, 900 cases were reported by 24 countries, with Estonia (0.82 per 100 000) followed by France (0.77 per 100 000) reporting the highest incidence.

 

Anthrax

 

Anthrax is a zoonotic disease caused by the bacterium Bacillus anthracis. Reservoirs are usually domestic and wild herbivores, and the spores can survive in the environment for decades. Anthrax is endemic in some regions in the world, including southern and eastern Europe. Humans become infected directly or indirectly from infected animals. Control measures include the correct disposal of animal carcasses, correct disinfection, decontamination and disposal of contaminated materials and the environment. The use of suitable protective equipment and vaccination of exposed susceptible animals and humans at occupational risk is required. Vaccine is limited to occupational, military and laboratory staff. B. anthracis has been recorded as a biological warfare agent since 1941.

 

Over the last 10 years, the overall incidence has been stable. Twenty-seven countries reported a total of 250 cases throughout the period (though only 24 countries reported for the whole 10-year period). The most cases were reported by Spain (65%), followed by Greece (14%). In 2005, 21 countries reported just 10 cases.

 

West Nile fever

 

West Nile virus (WNV) is related to other viruses causing encephalitis in humans. WNV is maintained in a cycle of wild birds and mosquitoes. Humans are mainly infected through mosquito bites, although infection through organ transplantation and blood transfusion has been documented, as has trans-placental transmission from mother to child. Since a first large outbreak in Romania in 1996, WNV infection has become recognised as a major cause of public health concern in Europe. No treatment or vaccine is currently available, and the main preventive measure is to minimise the risk of mosquito bites, using mosquito repellent and protective clothing when outdoors.

 

In the past 10 years, indigenous WNV outbreaks have been documented in the Czech Republic (1997) and France (2003) affecting five and seven cases respectively. In addition, sporadic imported cases have been reported in several European countries. The origin of infection of most imported cases is the USA, where an increasing number of infections have been reported since 1999.

 

Rabies

 

Rabies is a disease caused by a rhabdovirus. It is mainly a disease of animals and it occurs worldwide in warm-blooded mammals. The transmission normally occurs through a bite from, or direct contact with saliva of, an infected animal. The disease is fatal as soon as typical symptoms appear. Prevention is possible by vaccination (before or after exposure). Preventive veterinary measures include proper vaccination of cats and dogs. Oral vaccinations to wild animals have proven effective in preventing the spread of disease within wild animal populations. In the last 10 years no more than seven cases per year were reported across the EU (total 21 cases). In 2005, five cases of rabies were reported by 22 countries; four of them from Germany and one from the UK. There is a risk of re-introduction of rabies in the EU via travelling or by the cross-border movements of infected animals.

 

6.3.7.3. Mainly imported diseases

 

Malaria

 

Malaria is caused by the parasite Plasmodium, and is transmitted to humans by mosquitoes. During the 20th century, malaria was eradicated from many temperate areas, including the whole of the EU. As a result, the disease is now essentially limited to tropical countries. The potential for malaria re-introduction in countries where it has been eradicated is of growing concern partly due to global climate change, as the malaria vectors are still present in previously endemic areas, including Europe. ‘Airport malaria’ is sometimes reported in relation to the inadvertent transport of infected mosquitoes from endemic areas. Due to the large number of imported cases in Europe, malaria surveillance is focused on travellers’ health.

Since 1995, France has accounted for a large proportion of the imported malaria cases to Europe, mainly through its close ties with several African, highly endemic, countries. Over the period, the overall incidence rates have ranged from 1.45 to 2.27 per 100 000 per year, with a steady decrease since 2000 (Figure 6.8).

 

Figure 6.8. Malaria trends in Europe

 

In 2005, 4 306 malaria cases were reported by 26 countries (France not reporting). The favourable trend in recent years contrasts with the increasing numbers of malaria seen in endemic countries. The fact that the trend of malaria cases in returning travellers is in decline despite the ever-growing numbers of Europeans travelling, suggests that travel prophylaxis recommendations are being applied with increasing success. Still, the risk for travellers to highly endemic areas remains significant.

 

Viral haemorrhagic fevers

 

Only those infections for which cases were reported in returning European travellers, or which have been identified as a threat in 2005, are discussed here below. The quality and availability of data on VHF differ from country to country. Some Member States’ annual reports document data on VHF in general, some on virus-specific infections, while others do not report VHF at all.

 

Dengue fever is endemic in Asia, the Pacific, the Caribbean, the Americas and Africa. Humans are infected with Dengue virus through mosquito bites. Current evidence indicates that repeated infection increases the risk of the more serious Dengue haemorrhagic fever (DHF). In several Asian countries, DHF has become a leading cause of morbidity and death, mainly in children. Imported cases of Dengue fever are not uncommon, and in recent years Germany has reported annually some 120–220 cases, the UK around 200–250 cases, and Belgium and Sweden 25–60 cases. According to available data, no cases of DHF were reported in 2005.

 

Lassa fever is endemic to West Africa. Rats are the reservoir of lassa virus; humans become infected through contact with their excreta. While about 80% of infections are asymptomatic, the remaining patients develop severe multi-system disease and up to 15% of the hospitalised cases may die. Individual short papers in Eurosurveillance reported on a total of five imported cases of Lassa fever in Europe in the past five years: two cases in the UK from Sierra Leone (2000 and 2003), one case in the Netherlands in 2000, also from Sierra Leone, and two cases in Germany in 2000 from Ghana or Côte d’Ivoire and Nigeria. No cases were reported in 2005.

 

Crimean-Congo haemorrhagic fever (CCHF) is endemic in several countries of Africa, the European continent and Asia. The virus is transmitted to humans through the bites of ticks. There is no specific treatment or vaccine available, and up to 30% of patients may die. In recent years, outbreaks have been reported in Turkey, Kosovo and Albania. Eurosurveillance reported one imported case of CCHF in the UK, in a traveller returning from Zimbabwe. No cases were reported in 2005.

 

Ebola and Marburg haemorrhagic fevers are caused by the ebolavirus and marburgvirus respectively, both belonging to the same filoviridae family. Both are rare diseases, but have potentially high death rates. Transmission of the viruses occurs from person to person through close contact with blood or body fluids. No treatment or vaccine is available for either disease. No Ebola or Marburg haemorrhagic fever cases have been reported in Europe in the past 10 years.

 

Yellow fever

 

Yellow fever virus (YFV) has caused large epidemics in Africa and in the Americas, and is endemic in some tropical areas of these regions. The virus is transmitted through bites of mosquitoes, which also represent the reservoir for the virus. No specific treatment is available for yellow fever, but prevention is possible through administration of a highly effective vaccine.

 

Yellow fever has not caused any outbreaks in Europe for more than a century. Only sporadic cases have been reported in travellers returning from endemic regions. In the last 10 years, one case was reported by Germany in 1999 (imported from Côte d’Ivoire), one from Belgium in 2001 (imported from Gambia), four from the UK in 1998, 2001 and 2005, and two cases from Ireland in 1998 and in 1999 (but there is no information on the source country of the UK and Irish cases).

 

Plague

 

In Europe no human plague cases have been reported for a long time. Given the severity of the disease and its clinical characteristics, it is unlikely that cases have been missed. Though relatively rare, the disease has a worldwide distribution and in the most recent years, a growing number of cases have been reported to the WHO. Presently, its only implication for European health systems is to counsel international travellers and be prepared to diagnose and treat the disease in returning travellers.