Risks related to a possible reduction of the waiting period for dogs after rabies antibody titration to 30 days compared with 90 days of the current EU legislative regime

Abstract

EFSA received a mandate from the European Commission to assess the risks related to a possible reduction of the waiting period after rabies antibody titration test to 30 days compared with 90 days of the current EU legislation, for dogs moving from certain non-EU countries to the EU. This Scientific Report assessed the probability of introduction of rabies into the EU through commercial and non-commercial movements of vaccinated dogs with a positive titration test (≥ 0.5 IU/mL) if the waiting period decreases from 90 to 30 days. Assuming that all the legal requirements are complied with, the risk of transmission of rabies through the movement of a vaccinated dog is related to the risk of introducing an animal incubating rabies that was infected before the day of vaccination or shortly after vaccination but before the development of immunity (21 days post-vaccination). Using published data on the incubation period for experimental and field cases in dogs and considering the rabies incidence data in certain countries, the aggregated probability for the annual introduction of rabies through dogs was assessed. Considering the uncertainty related to the duration of the incubation period, the number of imported dogs, and the disease incidence in some countries it was concluded with a 95% certainty that the maximum number of rabies-infected imported dogs complying with the regulations in a 20-year period could increase from 5 to 20 when decreasing the waiting period from 90 to 30 days. Nevertheless, the potential impact of even a small increase in probability means the risk is increased for a region like the EU where rabies has long been a focus for eradication, to protect human and animal health.

Keywords: antibody titration test; dog; import; rabies; vaccination; waiting period.

Figure 1

Schematic representation of the two options of the lengths of the waiting period (current of 90 days and proposed of 30 days) after the sampling and before travelling, given that the titration test is positive (≥ 0.5 IU/mL). In addition, some other time intervals are included for both options to support the comparison; pv: post‐vaccination

Figure 2

Timeline showing the window of susceptibility for RABV infection and the period when dogs are considered protected from RABV infection due to the development of the immunity in relation to the moment of vaccination (V) and the waiting period of 30 (WP30) and 90 days (WP90). Dogs are assumed to be protected against infection from day 21 post‐vaccination (21dpv)

Figure 3

The process to be followed and the decisions to be taken in each step, for a dog to be allowed to enter the EU territory from non‐EU countries for which the specific condition for rabies antibody titration test applies as per Part I of Annex VIII to Commission Implementing Regulation (EU) 2021/404. The box representing clinical examination is not applicable for non‐commercial movements of dogs. MindMup app has been used to generate this figure

Figure 4

Map of non‐EU Countries from which dogs are allowed to travel to EU territory either with health certificate (orange) or with health certificate and rabies antibody titration test (red) according to Part I of Annex VIII to Commission Implementing Regulation (EU) 2021/404. ArcMap was used to create this map

Figure 5

Range from the time of inoculation to the time of the onset of clinical signs (blue) and death (red), respectively, in each group of dogs of the experimental trial in studies retrieved from the literature review

1. Each group of dogs has a unique identification code and was inoculated with different doses of RABV through intramuscular (IM), intracerebral (IC) and intranasal (IN) route. Black dots indicate the time to the onset of clinical signs and death individually for each dog of the group. For the group with code number W/1, the last dog died 257 days post‐inoculation but to maintain better visualisation of the whole graph the x‐axis is not extended up to the value 257.

Figure 6

Probability density of the duration of the incubation period (Crozet et al., 2022)

Figure 7

(Cumulative) Distribution of the number of days of the incubation period upon intramuscular challenge with rabies virus in unvaccinated dogs

Figure 8

Distribution of the duration of the incubation period (days) of rabies derived from experimental data from the literature review (red) and field data from Crozet et al. (2022) (green line). A log normal distribution was fitted to the datasets

Figure 9

Probability of an individual dog imported being infected and having an incubation period exceeding the waiting period of 30 days and 90 days accordingly, as a function of the incidence rate of rabies in the regions of dog origin

1. The Incidence Rate (IR) is calculated as the number of infected dogs per 100,000 dogs per year. When the incubation period is derived from the experimental data and the waiting period is 90 days, the individual probability is zero regardless the value of the IR.

Figure 10

The overall annual probability of at least one RABV‐infected dog with an incubation period exceeding the waiting period of 30 days and 90 days by the incidence rate of rabies in the regions of dog origin

1. Incidence Rate (IR) is calculated as the number of infected dogs per 100,000 dogs per year. When the incubation period is derived from the experimental data for a waiting period of 90 days, the individual probability is zero regardless the value of the IR.