Studies on Resistance of Embryonated Eggs, First-Stage Larvae, and Free-Living Infective Larvae of Metastrongyus apri to Different Temperatures

돈폐충(豚肺蟲) 자충(仔蟲)의 온도저항성(溫度抵抗性)에 관(關)한 연구(硏究)

In this study two sets of experiments were undertaken. Firstly, the embryonated eggs and first-stage larvae, sprayed in disinfected soil, were exposed to different temperatures. Then, the viabilities of them were weekly determined by inoculating the soil to earthworms, Eisenia foetida. Secondly, the infective larvae, seperated from the earthworms and suspended in tap water, were also exposed to different temperatures and their viabilities were checked microscopically at weekly intervals. The results were summerized as follows: 1. The maximum longevities of embryonated eggs and first-stage larvae were determined as 1 week at $35^{\circ}C$, over 36 weeks at $25^{\circ}C$, $15^{\circ}C$, and $5^{\circ}C$, 32 weeks at $-5^{\circ}C$, and under 1 week at $-15^{\circ}C$. 2. The mean numbers of infective larvae detected from the test earthworms were greatest at $5^{\circ}C$, and decreased with rise or fall of the temperature. 3. Infective larvae freed from the intermediate host were able to survive for 2 weeks at $25^{\circ}C$ and 3 weeks at $15^{\circ}C$. However, they lost their viabilities in a week at $35^{\circ}C$, $5^{\circ}C$, $-5^{\circ}C$, and $-15^{\circ}C$. 4. The number of living infective larvae at $15^{\circ}C$ was greater than at $25^{\circ}C$.