Ligula intestinalis (Cestoda: Diphyllobothriidae) in Kenya: a field investigation into host specificity and behavioural alterations

Genetic, haplotype and phylogenetic analysis of Ligula intestinalis by using mt-CO1 gene marker: ecological implications, climate change and eco-genetic diversity

Abstract Ligula intestinalis is a cestode parasite that affects freshwater fish in different countries of the world. The current study aims to reveal the phylogenetic, genetic and haplotype diversity of mt-CO1 gene sequences sent to the NCBI database from different countries by using in-silico analysis. The 105 mt-CO1 (371 bp) gene sequences of L. intestinalis obtained from NCBI were used for bioinformatics analyses. Sequences were subjected to phylogenetic and haplotype analysis. As a result of the haplotype analysis of L. intestinalis, 38 haplotypes were obtained from 13 different countries. Hap24 constituted 44.76% of the obtained haplotype network. Changes in nucleotides between haplotypes occurred at 1-84 different points. China and Turkey have highest fixation index (Fst) values of 0.59761, while the lowest (-0.10526) was found between Russia and Turkey. This study provides a baseline for future studies on extensive scale on the epidemiology, ecological aspects, distribution pattern, transmission dynamics and population dispersion of L. intestinalis worldwide.

Parasite Communities of Oreochromis niloticus baringoensis (Trewavas, 1983) in Relation to Selected Water Quality Parameters in the Springs of Lorwai Swamp and Lake Baringo, Kenya

PURPOSE

Parasite infections may lead to mortalities in fish; therefore, destabilizing the biodiversity and ecosystem functions. Swamps such as the Lorwai Swamp are important water sources, and information on the parasite species infecting Oreochromis nilotocus baringoensis in the hot springs of Lorwai Swamp which have a distinct genetic makeup from their counterparts in Lake Baringo is lacking. The purpose of this study was to provide a knowledge base on the parasite species infecting O. niloticus baringoensis in these springs, facilitate their comparison with those in Lake Baringo and determine their relationship with selected water quality parameters.

METHODS

347 fish were collected and standard parasitological procedures were used to examine the presence of parasites. Physico-chemical parameters were measured in situ and water samples were collected for chlorophyll-a determination and nutrient analyses in the laboratory using standard methods. Relationship between parasitic infections and selected water quality parameters was determined by PCA using SPSS version 22.

RESULTS

Two parasite species were common in all sites: Cichlidogyrus sclerosus and Clinostomum sp. Some parasites correlated positively with some parameters; Amirthalingamia macracantha and Contracaecum sp. with nitrogen compounds. Others like Clinostomum sp. and Tylodelphys sp. correlated negatively with dissolved oxygen.

CONCLUSION

Results from this study showed that there were both positive and negative relationships between some water quality parameters and the prevalence of recovered parasites. O. niloticus baringoensis from Lake Baringo also recorded high parasite prevalence and this calls for sensitization of the public on the risks that may arise from the consumption of undercooked infected fish.

Levels of heavy metals in the straightfin barb Enteromius paludinosus (Peters 1852) from River Malewa, Naivasha, Kenya

There have been several studies on heavy metals in Lake Naivasha. However, none of them has reported the levels of mercury (Hg), arsenic (As), and chromium (Cr). Moreover, there are no studies on the heavy metals' concentrations in the straightfin barb (Enteromius paludinosus, Peters 1852), a fish species that hosts a parasite (Ligula intestinalis), the latter having been reported to have a high ability to absorb heavy metals from its host. This paper therefore addresses the accumulation of heavy metals, namely arsenic (As), chromium (Cr), lead (Pb), and mercury (Hg) in the tissues of straightfin barb, Enteromius paludinosus (Peters 1852) from the mouth of River Malewa in Lake Naivasha, Kenya. A total of 1307 fish were collected during the month of November 2017. Water samples, sediment samples, 25 fish muscle tissues, and its endoparasite, the cestode Ligula intestinalis, were isolated, and heavy metal concentrations were determined using the thermal-electron atomic absorption spectrophotometer at the Lake Nakuru Water Quality Testing Laboratory. The concentrations of heavy metals in the sediment were below the lowest effect level in sediment, threshold effect concentration in sediment, severe effect concentration in sediment, and the shale values of sedimentary rocks thus showing no sign of pollution. In the muscle tissues of the fish, As, Cr, Pb, and Hg showed high levels with mean concentrations of 5.0696, 22.0854, 45.2108, and 1.5458 mg/kg ww, respectively. Bioconcentration factors further supported the observation that trace element accumulation was higher in fish compared with sediment and water. The target hazard quotients of As, Cr, Pb, and Hg obtained for both the female and male were > 1 indicating a possible health risk associated with the consumption of E. paludinosus. The bioaccumulation factors (BAFs) for L. intestinalis were 2.4093, 2.1873, 5.8601, and 5.1395 for As, Cr, Pb, and Hg, respectively, indicating the potential of the cestode in the accumulation of heavy metals from the host; hence, it can be used as an accumulation bioindicator.

Infection Status with Plerocercoid of Ligulid Tapeworm in Cyprinid Fish from Three Lakes in Republic of Korea

We have investigated freshwater cyprinid fish for its current infection status with plerocercoid of ligulid tapeworm in the Republic of Korea. A total of 6,049 (517 Euiam Lake and 4,071 Hoengseong Lake in Gangweon-do and 1,461 Chungju Lake in Chungcheongbuk-do) fish were examined by dissecting the peritonial cavity between March 2015 and December 2016. Totally 45 (0.74 %) fish in of 5 (26.3 %) species (8 Squalidus japonicus coreanus, 6 Squalidus gracilis majimae, 7 Opsariichthys uncirostris amurensis, 15 Zacco platypus and 9 Erythroculter erythropterus) were infected with plerocercoids of ligulid tapeworm. The infection density with plerocercoids in Erythroculter erythropterus was 12 – 26 per fish infected in Erythroculter erythropterus, and 1 – 2 in other 4 fish species. The plerocercoid was ivory-white and 26.2 – 57.8 cm long. The prevalence value in this survey was 0.9 % (45/6,049). The genetic analysis in this study was conducted to identify plerocercoid species. Based on genetic analysis with data in GenBank, these plerocercoids were identified as the L. intestinalis.

Spatial and temporal distribution of Ligula intestinalis (Cestoda: Diphyllobothriidea) in usipa (Engraulicypris sardella) (Pisces: Cyprinidae) in Lake Nyasa

Engraulicypris sardella is an endemic and economically important cyprinid species in Lake Nyasa/Malawi which has recently been infected by the tapeworm Ligula intestinalis. This parasite is known to induce severe pathological and behavioural effects on other cyprinids, including castration, followed by a collapse of infected populations. As a first step to understanding the dynamics between this parasite and E. sardella, we studied the spatial and temporal variation in prevalence over a period of 1 year. Overall prevalence was about 15%, but we observed a consistently higher prevalence in the littoral compared to the pelagic zone. Fish in the upper water levels showed the highest prevalence, with a marked decline with increasing water depth down to 150 m. The proportion of infected fish varied over time, with a significantly higher prevalence in the rainy season. In a huge lake like the Nyasa, with a surface area of 29,000 km2 and a maximum depth of 785 m, the transmission success of the parasite appears to show large variations in time and space. We suggest that these conditions could lead the parasite to become persistent within the lake, rather than the typical epidemic situation as observed in smaller bodies of water.

Mass Death of Predatory Carp, Chanodichthys erythropterus, Induced by Plerocercoid Larvae of Ligula intestinalis (Cestoda: Diphyllobothriidae)

We describe here the mass death of predatory carp, Chanodichthys erythropterus, in Korea induced by plerocercoid larvae of Ligula intestinalis as a result of host manipulation. The carcasses of fish with ligulid larvae were first found in the river-edge areas of Chilgok-bo in Nakdong-gang (River), Korea at early February 2016. This ecological phenomena also occurred in the adjacent areas of 3 dams of Nakdong-gang, i.e., Gangjeong-bo, Dalseong-bo, and Hapcheon-Changnyeong-bo. Total 1,173 fish carcasses were collected from the 4 regions. To examine the cause of death, we captured 10 wondering carp in the river-edge areas of Hapcheon-Changnyeong-bo with a landing net. They were 24.0-28.5 cm in length and 147-257 g in weight, and had 2-11 plerocercoid larvae in the abdominal cavity. Their digestive organs were slender and empty, and reproductive organs were not observed at all. The plerocercoid larvae occupied almost all spaces of the abdominal cavity under the air bladders. The proportion of larvae per fish was 14.6-32.1% of body weight. The larvae were ivory-white, 21.5-63.0 cm long, and 6.0-13.8 g in weight. We suggest that the preference for the river-edge in infected fish during winter is a modified behavioral response by host manipulation of the tapeworm larvae. The life cycle of this tapeworm seems to be successfully continued as the infected fish can be easily eaten by avian definitive hosts.

Dynamics and effects of Ligula intestinalis (L.) infection in the native fish Barbus callensis Valenciennes, 1842 in Algeria

The dynamics of the emergence, duration, and decline phases in epizootic cycles are well known for humans and some crops, but they are poorly understood for host-parasite systems in the wild. Parasites may be particularly insidious as they are often introduced unintentionally, simultaneously with their hosts, and later transferred to species in the new location. Here we investigate the epizootic dynamics of the tapeworm Ligula intestinalis in the Hamiz reservoir, Algeria, and explore its effects on the cyprinid fish Barbus callensis. Regular sampling was conducted from October 2005 to February 2008 with intermittent surveys carried out until 2010. Five percent of the 566 specimens of B. callensis that were caught were infected, with the maximum number of parasites found in spring. There was no obvious difference in weight between uninfected fish and infected ones, and infection did not affect fish condition. However, infected fish were significantly longer than uninfected fish and had inhibited gonad development. The proportion of infected fish caught was significantly higher in year 1 and by the second winter, infection collapsed to zero. The Ligula infection thus appeared to have minimal ecological effects and be of a temporary nature, thus exhibiting an epizootic cycle. Taken together, our data indicates that this infection declined or even failed during our study period. Failure may be due to the specific genetic strain of Ligula, but invasive carp may also have been influential in both the introduction and subsequent decline of this parasite.

Parasites of commercially important fish from Lake Naivasha, Rift Valley, Kenya

In Lake Naivasha, the common carp Cyprinus carpio L. 1758 was accidentally introduced from fish farms adjacent to River Malewa in 1999 and now forms the bulk of the total fish caught. Since its introduction, no study has been made on its parasitic community nor are there any reports on ectoparasites from other fish species in this lake to the best of our knowledge. Therefore, the aim of this study was to describe the parasitic community of C. carpio and two other commercially important fish species: Oreochromis leucostictus and Tilapia zillii. Additionally, the abundant Barbus paludinosus was included in the study. A total of 286 fish (145C. carpio, 56 O. leucostictus, 18 T. zillii, and 67 B. paludinosus) were collected during the year 2011 and examined. Ten taxa of parasites were recovered from C. carpio dominated by the monogenean Dactylogyrus minutus, occurring with a prevalence (p) of 99.3%. Thirteen taxa of parasites were identified from O. leucostictus dominated by monogeneans Cichlidogyrus spp. (p = 91.1%). T. zillii harbored nine taxa of parasites with the digenean Tylodelphys sp. (p = 83.3%) being dominant and B. paludinosus harbored 11 taxa of parasites dominated by an unidentified monogenean of the genus Dactylogyrus (p = 83.6%). C. carpio had the lowest helminth species diversity and richness while monogenetic trematodes, which have never been reported from fish in Lake Naivasha, were the most prevalent parasites recovered.

Ligula intestinalis (Cestoda: Pseudophyllidea): an ideal fish-metazoan parasite model?

Since its use as a model to study metazoan parasite culture and in vitro development, the plerocercoid of the tapeworm, Ligula intestinalis, has served as a useful scientific tool to study a range of biological factors, particularly within its fish intermediate host. From the extensive long-term ecological studies on the interactions between the parasite and cyprinid hosts, to the recent advances made using molecular technology on parasite diversity and speciation, studies on the parasite have, over the last 60 years, led to significant advances in knowledge on host-parasite interactions. The parasite has served as a useful model to study pollution, immunology and parasite ecology and genetics, as well has being the archetypal endocrine disruptor.