Department of Wildlife, Fisheries and Aquaculture, Mississippi State University, Mississippi State, Mississippi 39762.
Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, Mississippi 39762.
J Parasitol. 2022 Mar 1;108(2):217-225. doi: 10.1645/20-123.
Advances in hybridization practices in U.S. catfish aquaculture have led to increased production of channel (Ictalurus punctatus) × blue catfish (Ictalurus furcatus) hybrids to capitalize on their more favorable production characteristics. However, the effects of typical channel catfish pathogens on hybrids are not well understood, including the digenean Bolbophorus damnificus, which has caused significant losses in channel catfish production. Three experiments were conducted to assess the longevity and site specificity of 2 life stages of B. damnificus impacting catfish production. The first experiment investigated the cercarial longevity and infectivity of B. damnificus over time. Channel catfish were individually challenged with 100 cercariae/fish with cercariae aged in 12-hr time intervals over 5 days (n = 5 fish/time point), with metacercarial cysts excised and enumerated 14 days postchallenge. There was a decrease in cercaria viability and encysted metacercariae over the first 36 hr, with the 12-hr time point having both the greatest cercaria survival and the highest number of metacercariae in exposed fish. The second experiment investigated the longevity of metacercariae within both channel and hybrid catfish. Fish (n = 30) were exposed to 2 treatments (75 or 150 cercariae/fish), and 2 fish from each treatment were sampled every 3 mo for 13 mo. Live metacercariae, based on motility observed after excystment, were found in both species up to 13 mo postchallenge, indicating the metacercariae of B. damnificus can persist throughout an entire growing season in both channel and hybrid catfish. The third experiment investigated the site specificity of metacercariae within both channel and hybrid catfish. Fish (n = 60/species) were challenged with 300 cercariae/fish and 9 fish/species were sampled after 90 days. Metacercariae were excised and enumerated from the anterior midsection (head and body), posterior midsection (trunk/caudal peduncle), ventral (belly), and caudal fin (tail) sections of each fish. Overall, the trunk/caudal peduncle had a 2-fold increase in the number of metacercariae excised, and although not significantly higher, results indicate this region should be the focal point of pondside assessment for the presence of B. damnificus because of ease of detection of encysted metacercariae.
美国鲶鱼养殖中杂交实践的进展导致了更多的斑点叉尾鮰（Ictalurus punctatus）× 蓝鲶（Ictalurus furcatus）杂交种的生产，以利用其更有利的生产特性。然而，典型的斑点叉尾鮰病原体对杂交种的影响尚不清楚，包括吸虫 Bolbophorus damnificus，它已导致斑点叉尾鮰生产的重大损失。进行了三项实验来评估影响鲶鱼生产的 2 种生活阶段的 B. damnificus 的寿命和部位特异性。第一项实验研究了 B. damnificus 的尾蚴寿命和感染力随时间的变化。用 100 个尾蚴/鱼挑战单独的斑点叉尾鮰，每隔 12 小时将尾蚴在 5 天内老化一次（n = 5 个鱼/时间点），在挑战后 14 天切除并计数囊蚴。在最初的 36 小时内，尾蚴的活力和囊蚴逐渐减少，12 小时时间点的尾蚴存活最多，暴露鱼体内的囊蚴数量最多。第二项实验研究了斑点叉尾鮰和杂交鲶鱼体内囊蚴的寿命。用 2 种处理方法（75 或 150 个尾蚴/鱼）暴露鱼（n = 30），并在 13 个月内每 3 个月从每个处理中取样 2 条鱼。在挑战后 13 个月，从两种鱼中都发现了可运动的活囊蚴，表明 B. damnificus 的囊蚴可以在整个生长季节都存在于斑点叉尾鮰和杂交鲶鱼体内。第三项实验研究了斑点叉尾鮰和杂交鲶鱼体内囊蚴的部位特异性。用 300 个尾蚴/鱼挑战鱼（n = 60/种），并在 90 天后对 9 种鱼/种进行采样。从每条鱼的前中部（头和身体）、后中部（躯干/尾柄）、腹部（腹部）和尾鳍（尾巴）中切除并计数囊蚴。总体而言，尾柄/尾柄的囊蚴数量增加了 2 倍，尽管没有显著增加，但结果表明，由于易于检测囊蚴，该区域应该是池塘边评估 B. damnificus 存在的重点。
