Hartmut Schlüter

Chance and risk of controlling rabies in large–scale and long–term immunized fox populations

The large–scale immunization of European fox populations against rabies is currently under the microscope for reducing the considerable expenditure without putting public health at risk. Empirical knowledge is inadequate to interpret the lasting sporadic incidences and, therefore, to verify the final success of the immunization campaigns. By using a proven simulation model we show that rabies can persist on a very low level in the form of spatio–temporal moving infection clusters within a highly immunized fox population. We found further: (i) the existence of a threshold after which the chance of eradicating the disease by vaccination increases clearly, and (ii) that at least six years of 70%mean immunization rate are required to guarantee a likely success.

Trends in the temporal and spatial distribution of visceral and cutaneous leishmaniasis in the state of Bahia, Brazil, from 1985 to 1999

Temporal and spatial trends in the geographical distribution of 12,413 cases of American visceral leishmaniasis (AVL) and of 48,138 cases of American cutaneous leishmaniasis (ACL) notified from 1985 to 1999 in the State of Bahia, Brazil, were analysed. The emergence of new endemic municipalities indicated an increasing trend for AVL and ACL. In the years 1985, 1990 and 1996, AVL was endemic in 7% (n = 31), 18% (n = 73) and 30% (n = 123), and ACL was endemic in 13% (n = 54), 27% (n = 112) and 34% (n = 140), of 415 municipalities. New trends were identified, and the relation with the ecoepidemiology of both diseases is discussed.

Standardisation and establishment of a rabies ELISA test in European laboratories for assessing the efficacy of oral fox vaccination campaigns.

A simple and rapid enzyme linked immunosorbent assay (ELISA) to detect rabies antibodies in field fox sera has been standardised and established in several European laboratories. The same panels of 100 coded sera were investigated by four laboratories using this ELISA assay and reference serum neutralisation techniques (fluorescent antibody virus neutralisation (FAVN) test and rapid fluorescent focus inhibition test (RFFIT)). This indirect ELISA technique is highly correlated with conventional seroneutralisation test on cell culture. Results obtained with this ELISA test provide an almost perfect agreement between laboratories while the agreement of FAVN test and RFFIT results is substantial and very satisfactory. In view of this study, this simple and rapid ELISA test is a suitable tool for evaluating the sero-conversion rate in fox populations following oral rabies vaccination campaigns in European countries.

Elimination of terrestrial rabies in Germany using oral vaccination of foxes

Oral rabies vaccination (ORV) has become the method of choice in fox rabies control in Europe. During the past three decades fox-mediated rabies virtually disappeared from Western and Central Europe. Following Switzerland, Germany was the second European country to launch ORV field trials on its territory in 1983. This paper provides a historical overview on the emergence of fox rabies in Germany; describing the basic principles and milestones of the German rabies eradication programme and presenting results of two decades of efforts to control the disease in foxes. Also, setbacks as well as country-specific differences and particularities on Germanys long way to rabies elimination in comparison to other European countries are addressed. Since the first field trials in Germany the number of rabies cases steadily decreased from 10 484 in 1983 to three cases recorded in 2006. On February 3rd 2006 the last case of terrestrial rabies in Germany was detected in a fox near the town of Mainz, Rhineland-Palatinate. In 2008, ORV ceased after 25 years and Germany was officially declared as free from terrestrial rabies. The German rabies eradication programme did cost approximately 100 million euro of which 37 million euro were covered by the EU. For the future, efforts should focus on maintaining a rabies free status by implementing measures to prevent reintroduction of terrestrial rabies from endemic countries.

Analysis of sampling strategies to substantiate freedom from disease in large areas

In this paper, we deal with the strategies of surveys to substantiate freedom from disease for a certain territory. Infection might not be distributed homogeneously. So, a relatively high within-herd prevalence might be observed while the herd-level prevalence is lower. For this situation, we compare various two-stage sample strategies. The calculation of appropriate sample sizes becomes quite complicated. The theoretical generalization of the hypergeometric distribution by Cameron and Baldock [Prev. Vet. Med. 24 (1998) 1] introduces a simple way to evaluate multi-stage sample sizes while regarding real-test properties. We demonstrate the theoretical foundations of these calculations. These principles open up the possibility of optimizing costs or other relevant variables, by choosing the appropriate sample strategy (each of which ensures the same alpha-level for the first stage). In addition, we evaluate the statistical power of the complete strategies under consideration.Furthermore, we apply our theoretical results to a data example of Brucella melitensis. We used the herd-size situation in Germany, characterized by many small sheep holdings and only a few large ones. The consequences of real-test properties on sample sizes and on the applicability of several strategies are discussed.