Rabies in Israel

Rabies (Lyssa) is rife in the Middle East since ancient times. The clinical symptoms have been detailed in old Hebrew manuscripts dating about 2000 years ago. Since the establishment of the State of Israel (Review 1948 - 1997), the occurrence of the disease in animals has been considerably decreased, due to severe control measures carried out under the provisions of the Rabies Ordinance, which - among others - prescribes the compulsory vaccination and the leashing of all dogs, and the muzzling of dogs in infected areas. The Rabies regulations prescribe the quarantining of biting animals and the Licensing & Vaccination of dogs. Since 1957, annual vaccination has become compulsory. Identification of pet dogs and cats is regulated by the local authorities (Sample by-law for local authorities).

Consequently, extensive safety and efficacy trials with available oral vaccines had to be carried out before releasing the selected vaccines into the environment. The project was planned in consultation with international experts and institutions, such as the WHO and CDC. The preliminary trials, in 1993 - 1994, involved the safety of the candidate vaccines for various non-target animals, mainly rodents, in order to exclude the potential hazard of them becoming involved in a viral cycle. The stability of the baits and of the candidate vaccines was tested in the typical climatic conditions prevailing in the region (exposure to solar radiation; high temperatures). The selected vaccines were consequently used in preliminary vaccination trials in foxes and jackals in captivity. These trials indicated that the oral vaccination of jackals needed further experimentation. The rabies issue was discussed in several regional animal-health meetings, as a priority subject for regional research project. Preliminary field trials, supported by foreign and local institutions were carried out during 1995/6 in 3 areas in Central Israel to evaluate the bait palatability for foxes and jackals (Summary, Linhart et al in 1997). During these trials, an extremely high density of jackals was demonstrated.

An epidemiological investigation based on molecular and antigenic characterisation of rabies virus from various regions in Israel has shown, that at least six genotypes of the rabies virus, characterised by distinct geographical distribution, are involved in the epidemiology of rabies in Israel (dendogram, map 1).

During 1996 - 1998 the incidence of rabies in wildlife showed a further increase. After an absence of human rabies in Israel for 25 years, three cases in humans were recorded in Northern Israel (November 1996 - December 1997).  Although the involved vectors have not been traced (all three victims were exposed while sleeping outdoors in rural areas) - circumstantial evidence indicated that they were, most probably, infected by small nocturnal wild animals or cat(s). The three human isolates and those isolated from infected wild carnivores in the same vicinity revealed 100% homology with a virus recovered from a fox (D. David et al). In light of this tragic development, the issue became acute; extensive media involvement and parliamentary discussions followed. Upon the suggestion of the Veterinary Services, a national task force was established on 6.1.98, including several  Ministries and public health related institutions. The Task Force, headed by the Chief Veterinary Officer, recommended to enhance the oral-vaccination activities and specified the essential necessary budget. The recommendations were accepted by the ministries involved - Agriculture and Environment. This led to budget becoming available for full-scale laboratory and field trials. These were carried out, in several stages, during 1998 at the Kimron Veterinary Institute, involving about 50 jackals and several (control) foxes. Two candidate vaccines were tested.

After the completion of the experimental trials, on animals in captivity, field trials followed during the first two trimesters of 1999. They included baiting from the air of the designated area of approx. 400 sq. km (2% of the area of Israel), in the Central Galilee (Pictures). The main conclusions of the researchers (B. Yakobson and R. King) were:

1. Foxes and jackals were susceptible to challenge in the laboratory  with the jackal rabies strain (Golan).
2. The duration of the clinical disease in challenged jackals was significantly longer than in foxes.
3. The two tested vaccines were found efficacious for the oral vaccination of jackals.
4. Two dispersals of the baited vaccine (Raboral-V-RG) with 6 months intermission, in the rate of 20 baits per sq/km, brought about the immunisation of 60% of the target animals (foxes and jackals), an immunisation rate generally regarded sufficient to discontinue the infection cycle.
5. The oral vaccination has brought the outbreak to a halt within the treated area.
6. Since, as molecular studies show, there are several different rabies virus genotypes in Israel, with a distinct geographical distribution (map 1), regionally arranged oral vaccination might be feasible.
7. It seems that at least five years of continuous oral vaccination might be necessary for a significant, countrywide reduction of rabies.

The success of the said field trial, in an area which had been heavily infected during several previous years, and the clear results of the experimental trials in captivity, paved the way to further budgeting and wide-scale trials during 2000, including additional areas in the northern and central parts of Israel (map 2 ).

Though definite results have not yet been summarised, it seems that a remarkable decrease in the incidence of rabies has been monitored (maps 1996, 1997, 1998, 1999, 2000 and first semester of 2001). This justifies an uninterrupted continuation of full-scale oral vaccination.

Rabies oral vaccination, in wildlife and/or in other vectors (stray dogs), will be subject to discussions within the regional animal-health bodies, hopefully to be included within the envisaged regional projects.