Studies on Anisakis Type Larvae

Anisakis 형(型) 유충(幼蟲)에 관한 연구(硏究)

As it has been known recently that anisakis type larvae harbouring in marine fishes are a causal agent of zoonosis to human and probably to land living mammal animals, attention was focused on the study on the larvae in an aspect of epidemiology or epizootiology. The present work was conducted from 1966 to 1975 for i) survey on the harbouring status of anisakis type larvae in marine fishes of this country, ii) observation on the response to the experimental infestation of the larvae to the pigs, in the reason that they could well fetid raw fish viscera occasionally containing the larvae as a high protein source of swine food, and iii) observation on the larval resistance and response to vermicidal agents for the purpose of prevention of the larval infection to the mammal animals. The data obtained in the studies were summarized as follows: 1. In the survey on the status of larvae harbouring in main species of marine fishes of this country, 15 species, a total of 1,940 fishes, were observed and the result was summarized in table 2. Average number of larvae, in upper rank of 5 out of all 15 species of fishes, were as highest as 156 larvae ranging 74 to 450 in Pseudosciaena manchurica (chamjogi), 54.5 ranging 15 to 240 in Trichiurus haumela (kalchi), 35.6 ranging 8 to 112 in Trachurus japonica (junggengi), 30.6 ranging 4 to 65 in Parapristipama trilineatum (benjari) and 20.5 ranging 3 to 48 in Nibea argentata (boguchi) respectively. In morphological observation, size of the larvae in the fishes were varied, ranging from 2 to 32mm long, and a tendency to larger size and number of larvae in the fishes, which were wider sea migration, higher age and lager bodily size, was observed The favorite places harbouring the larvae in fishes were mainly around the intraperitoneal viscera such as mesentery, omentum, liver, pyloric suspensory, fat tissue and cloaca, and rarely in body muscles of fish. Fishes heartily infested with the larvae showed stunted growth decreased egg formation and severe damage of liver. 2. In the experimental infestation of the larvae to normal pigs, as illustrated in table 3, a group with large dose of larvae (a total of 1,800 larvae, 300 larvae Per dose, twice in a dart for 3 days) showed acute clinical syndrome terminatine death with a week course, whereas two groups with less dose of larvae (a total of 180~360 larvae, 10 larvae per dose, at 5 days interval for 70~180 days) showed subclinical syndrome with remarkably stunted growth as. much as approximately one half of body size in contest to the control pigs. In the pathological findings, a group with large dose of larvae showed macroscopically larvae penetrating to the gastric wall with severe gastroenteritis, and histopathologically various acute lesions caused by active larvae penetration into the wall of stomach and interstine, whereas two groups with less dose of larvae showed chronic lesions such as hypertrophy and verminous granulomatous swelling of gastric wall, suggesting strongly the possibility of natural infestation of larvae to swine. 3. In the resistance of the larvae to the chemical solutions, the larvae tolerated for 2 days in 15 percent solution of sodium chloride and acetic acid, and for 7 days in 70 percent solution of ethyl alcohol. In the resistance to the temperature, the larvae died within 1 second at $62^{\circ}C$ and tolerated for 24 hours at $-3^{\circ}C$, 12 hours $-5^{\circ}C$ respectively. 4. For the experiment on the vermicidal effect to larvae, general vermicidal drugs such as Neguvon, Combantrin, antimony Potassium, piperazine adipate and piperazine dihydrochloride, oxidizer such as potassium permanganate and potassium chlorate, and dyes such as gentian violet and crystal violet were used, and among them, as illustrated in table 6, potassium permanganate was proved as the best. In the successive test for the practical use of potassium permanganate, vermicidal effect in seawater solution of potassium permanganate and common-water solution of potassium permanganate were compared, and then retested by dipping the fish viscera including the larvae into the two different solutions of potassium permanganate. The result through these tests indicated that 0.01 percent common water and sea-water solution of potassium permanganate could be apparently recommended as a preventive vermicidal solution, having 90 to 100 percent vermicidal effect by dipping for 12 to 24 hours even though sea-water solution of potassium permanganate had a tendency to slightly less effect than the common-water solution of potassium permanganate (Table 8).