European Bat Lyssavirus Transmission among Cats, Europe

We identified 2 cases of European bat lyssavirus subtype 1 transmission to domestic carnivores (cats) in France. Bat-to-cat transmission is suspected. Low amounts of virus antigen in cat brain made diagnosis difficult.

was bitten by cat no. 1 received a booster rabies vaccination, and 15 persons exposed to cat no. 2 during the 2-week critical period before its death received appropriate postexposure treatment on the basis of national and international recommendations of the World Health Organization (8,11). Two family dogs potentially exposed to cat no. 2 and previously vaccinated received a booster vaccination. Crossneutralization data obtained with human serum samples and in rodent models suggest that preexposure and postexposure treatments for rabies are effective against EBLV-1.
Control measures were implemented to prevent potential further contaminations, although cats represent naturally dead-end host for rabies (and for lyssavirus), thereby limiting any risk for transmission to other mammals. City authorities conducted a census of all domestic animals in the neighborhood where cat no. 2 lived. All cats, dogs, and ferrets were identifi ed by microchips and kept under veterinary surveillance. Dogs had to be leashed and cats kept indoors during the next 2 months.

Conclusions
We report 2 documented cases of natural infection of domestic cats by EBLV-1 lyssaviruses presently circulating in European bats (2)(3)(4)(5). Our study demonstrates that subtypes EBLV-1a and EBLV-1b can cross the species barrier, although cat no. 1 probably died of feline leukemia. However, cat no. 2 died with neurologic signs compatible with rabies and was positive for EBLV by FAT, the reference technique. Direct transmission of EBLV-1 from bats to cats seems the most realistic explanation for these cases because cats prey on bats and have numerous contacts with them (3,12,13). Identifi cation of a highly homologous EBLV-1a isolate from a rabid bat found in the same location as cat no. 2 supports this hypothesis.
Diffi culties in EBLV-1 detection in the brain of these 2 cases of spillover transmission are reminiscent of transmission previously reported (6,7) (Table 1), potentially caused by a low amount of virus antigen in the brain. This fi nding further underlines the importance of using different techniques to diagnose rabies caused by EBLVs (9). This issue raises questions about the true incidence of these viruses among cats.
At the Institut Pasteur during 1997-2007, a total of 6,097 cats suspected of having rabies and originating from all districts in France showed negative results for rabies by 2 recommended techniques (FAT and RTCIT). Among them, all animals tested since 2004 (1,506 cats), except cats no. 1 and no. 2, were also negative for rabies by WELYS-SA ( Figure 2), which suggests that transmission of EBLVs from bats to cats, although possible, is rare. Furthermore, terrestrial mammals seem to represent dead-end hosts for EBLVs, as suggested by results of experimental EBLV inoculations in several mammals such as cats, dogs, ferrets, mice, red foxes, or sheep (6,7,14). These animals are susceptible to infection with EBLVs but seem unlikely to actively transmit EBLVs to a new host.
Comparative analysis of the full-length genomic sequence of the EBLV-1a from cat no. 2 isolate 07240FRA   with bat isolate 08120FRA and with another bat (E. serotinus) isolate (03002FRA) collected in 2003 ≈100 km from Fontenay-le-Comte showed high similarity (Table 2). This fi nding indicates that heterologous passage of EBLV-1a in a cat did not select mutants. Similarly, the lower similarity observed with a genomic sequence collected from a bat RV9 (15) (E. serotinus) in 1968 in Germany also indicates that EBLV-1 evolution is shaped by slow genetic drift (2). No secondary cases originating from cat no. 1 and cat no. 2 were reported (after 6 months of follow-up for cat no. 2). However, improving surveillance and raising awareness to better understand the epidemiology of lyssaviruses are necessary. Persons bitten by bats or by any carnivorous animal are advised to wash wounds with water and soap and to seek medical attention (8,11). by direct immunofl uorescence antibody test, rabies tissue culture infection test, and an antigen-capture ELISA is given by district. Precise location of the 2 infected index (positive) cats and positive bats (n = 32) are indicated by circles and triangles, respectively, and associated with numbers 1, 2, 3, and 4 for isolates 03011FRA, 03002FRA, 07240FRA, and 08120FRA, respectively. EBLV-1a and EBLV-1b isolates are indicated in black and white, respectively. Map was constructed by using Articque's C&D software (www.articque. com) and published according to Articque's publication policy.