Assessing the risk of an emerging zoonosis of worldwide concern: anisakiasis

Abstract

Anisakiasis is an emerging zoonosis caused by the fish parasitic nematode Anisakis. Spain appears to have the highest reported incidence in Europe and marinated anchovies are recognised as the main food vehicle. Using data on fishery landings, fish infection rates and consumption habits of the Spanish population from questionnaires, we developed a quantitative risk assessment (QRA) model for the anchovy value chain. Spaniards were estimated to consume on average 0.66 Anisakis per untreated (non-frozen) raw or marinated anchovy meal. A dose-response relationship was generated and the probability of anisakiasis was calculated to be 9.56 × 10^-5 per meal, and the number of annual anisakiasis cases requiring medical attention was predicted between 7,700 and 8,320. Monte Carlo simulations estimated post-mortem migration of Anisakis from viscera to flesh increases the disease burden by >1000% whilst an education campaign to freeze anchovy before consumption may reduce cases by 80%. However, most of the questionnaire respondents who ate untreated meals knew how to prevent Anisakis infection. The QRA suggests that previously reported figures of 500 anisakiasis per year in Europe is a considerable underestimate. The QRA tool can be used by policy makers and informs industry, health professionals and consumers about this underdiagnosed zoonosis.

Figure 1. Value chain and process model outline for untreated raw and marinated home-prepared anchovy.

Figure 2. Probability density function of the number of viable Anisakis spp. consumed per untreated anchovy meal with 100% viability (mean 0.66, SD 1.15).

Figure 3. (i) Dose response for Anisakis spp. (ID50, mean 17,000, SD 14,000), (ii) inset of dose response at higher resolution for low doses (i.e. exposure between 1 and 10 parasites).

Figure 4. Probability density function of the probability of disease (anisakiasis) per untreated anchovy meal (mean 9.56 × 10⁻⁵, SD 3.68 × 10⁻⁴).