High occurrence of Anisakidae at retail level in cod (Gadus morhua) belly flaps and the impact of extensive candling

The presence of Anisakidae at retail level, after the routine screening via candling, was investigated in cod, the most commonly consumed fish species in Belgium. A total of 780 pre-packed belly flap samples destined for one branch of retail shops were collected from a Belgian wholesale company. To recover all larvae, each sample was first candled and thereafter enzymatically digested. Larvae were morphologically identified to the genus level and a subset was additionally molecularly confirmed by amplification of the ITS fragment and HinfI/HhaI enzyme restriction. The PCR/RFLP profiles of Contracaecum spp. were determined and confirmed with sequencing by the European Reference Laboratory for Parasites (Istituto Superiore di Sanità). The positivity rate of Anisakidae in the individual cod samples was 18% [95%-CI: 15–21%], with a mean intensity of one larva [range: 1–6]. Belly flaps were sold packed primarily by two, with a one-in-three chance of buying an infected package. Pseudoterranova spp. infections (single infections) were most frequently detected (positivity rate 9% [95%-CI: 7–11]), closely followed by Anisakis spp. (7% [95%-CI: 6–9]). Co-infections of Pseudoterranova spp. and Anisakis spp. comprised 8% of the infections, with a positivity rate of 1% [95%-CI: 1–3%]. All belly flaps reportedly were candled prior to our sampling, nonetheless our results indicated that an additional candling screening before packaging would identify an extra third of the infections and larvae. In 19 of the 139 infected samples, all larvae were recovered by the additional candling, thereby removing the infection risk for consumers. In conclusion, this study shows that cod belly flaps infected with zoonotic parasites reach the Belgian consumer. Although a second candling step at retail level could be helpful in reducing the consumer risk, additional measures are needed since 66% of infections would still remain undetected

Preliminary evaluation of different methods to detect and quantify <i>Taenia</i> eggs in sludge and water samples: A spiking experiment to assess recovery efficiency.

An improved understanding of the environmental transmission of Taenia spp. is key to control of the parasite. Methods to detect and quantify Taenia eggs in different environmental matrices, including sludge and water, currently lack performance validation with regard to the recovery efficiency and process ease of use. Therefore, this study aimed to assess the recovery efficiency and process duration of commonly used methods for the detection of Taenia eggs in sludge and water samples. Ten detection methods for Taenia spp. eggs were selected from a systematic review. Sludge and water samples were spiked with a high dose of Taenia saginata eggs, i.e., around 200 eggs/g sludge and 50 eggs/ml water, and were tested using five methods each. The two methods with the highest egg recovery efficiencies were selected per matrix for assessment with a lower spiking dose, i.e., 4 eggs/g sludge and 1 egg/ml water. Each time five replicates were used. Recovery efficiency was defined as the proportion of the number of eggs recovered to the total number of eggs spiked. Using the high spiking dose, all samples tested positive for all the methods. The mean egg recovery efficiency varied from 4% to 69% for sludge samples and from 3% to 68% for water samples. Using the lower spiking dose, one of the methods performed on sludge samples was able to detect all replicates, whereas only one replicate was positive using the other method. For water, all low dose samples tested positive using both methods. In conclusion, most methods performed inadequately in recovering Taenia eggs from sludge and water, with half of the methods performed on the high dose samples having a mean egg recovery efficiency of approximately 10% or less. The assessed recovery methods were generally time-consuming and labourious. A more thorough validation of existing recovery methods and improvement of method protocols to increase recovery efficiency is thus urgently needed

Ascaridoids in commercial fish : occurrence, intensity and localization in whole fish and fillets destined for the Belgian market

Anisakidae and Raphidascaridae are marine nematodes present in a wide range of fish hosts, which may cause gastro-intestinal complaints and/or allergy in human, in addition to economic losses for the industry. Data regarding the presence of these parasites in fish for the Belgian market is currently missing; therefore, our aim was to investigate the presence and intensity of ascaridoids in a wide range of commercially fish species. A total of 415 fish samples, belonging to 36 different fish species, were collected from a Belgian whole-sale company. Ascaridoid larvae from the viscera (if present) and the muscles were collected by enzymatic digestion and the prevalence, median intensity, mean number of larvae per 100 g infected muscle, and localisation were determined. An overall prevalence of 53% [95%-CI: 42–63%] in the viscera and 27% [95%-CI: 23–32%] in the muscles was observed. Infection in the muscles varied between the fish species; no larvae were detected in 13 fish species, while a high prevalence (>78%) was observed in pollack, halibut, and gurnard. Most samples originated from the Northeast Atlantic Ocean, with the highest prevalence in the muscles observed in the Barents & Norwegian Sea (65% [95%-CI: 38–86]). Muscle samples were, if possible, divided in an anterior region, belly flap, medial region, and posterior region, with the most infections and larvae found in the belly flaps. In all samples, a total of 2569 larvae were recovered, with 1594 larvae originating from the viscera and 975 from the muscles; with an average of two larvae per 100 g infected fillet detected. Larvae were morphologically identified, and a subgroup was further confirmed using PCR/RFLP, resulting ultimately in the identification of Anisakis simplex s.s. (1853 larvae), A. pegreffii (137), A. simplex/pegreffii hybrid genotype (38), Pseudoterranova decipiens (160) and Hysterothylacium aduncum (380). This study demonstrates that ascaridoid larvae are highly prevalent in different fish species on the Belgian market

Sensitivity of candling as routine method for the detection and recovery of ascaridoids in commercial fish fillets

Ascaridoids are one of the main parasitic hazards in commercial fish. Candling is the current industrial screening method whereby visible ascaridoid larvae are detected on a light table and manually removed. The aim of this study was to assess the sensitivity (Se) and negative predictive value (NPV) of this method. To make targeted recommendations to the fish industry, the Se was calculated per fish part, larval genus, and fish species. All fish parts (n = 615) were first candled, and larvae were collected, followed by enzymatic digestion to recover the remaining larvae. A fish part was considered positive if at least one larva was detected using candling and/or enzymatic digestion, with both methods combined as reference standard. The overall Se of candling was 31% (95% CI 23-41%) and NPV was 87% (95% CI 85-90%). The Se increased with higher numbers of larvae/100 g infected muscle. A low NPV was found for the belly flaps, therefore we either advise the removal or proper freezing of this part. Lastly, the Se and larval recovery was the highest for the darker and larger Pseudoterranova spp. larvae. Due to the low overall efficacy of candling, further assessment of its cost-benefit and impact on consumers' health risk should be conducted