The Caspian Sea with the lower reaches of the rivers flowing into it are Kazakhstan’s most important fisheries. Here there are about 0.3 million tons of fish caught annually. Fish parasitoses act as a potential factor restraining the growth of fish productivity. Some helminths of fish may also be zoonoses and therefore represent a public health problem. Therefore the study of parasites presently infecting fish in the Caspian Sea basin may provide important information to reduce the risk of spreading economically important diseases of fish in the region. Such studies may also contribute to ameliorating the public health risk of some helminths. Furthermore we aimed to identify potential pathogenic effects by analyzing the association of Fulton’s condition index with the intensity of infection with parasites identified.
The Caspian fisheries are of commercial importance. There are a number of studies from the southern sectors of the Caspian, mainly from Iran (eg Khara et al., 2011; Sattari
The purpose of the work is to study the distribution of
To determine the infection with anisakidosis and other potentially zoonotic parasites, 606 fish were investigated from the Kazakhstan sector of the Caspian Sea (Fig. 1). For each of 12 species, 50 fish were examined (Tables1 – 4). For one species, the European catfish
The number of fish infected and range of intensity of infection of parasites in fish of order Clupeiformes.
Fish host | Parasite | Number infected (prevalence, confidence intervals) | Development stage of parasite recovered and localization | Range of intensity | Mean abundance | Parasite Taxon |
---|---|---|---|---|---|---|
1 (2, 0.1 – 11) | Third stage larva (Abdominal cavity, muscle, serous membrane) | 2 | 0.04 | Nematoda: Anisakidae | ||
6 (12, 5 – 24) | Third stage larva (Abdominal cavity) | 1 – 4 | 0.2 | Nematoda: Ascaridoidea | ||
1 (2, 0.1 – 11) | Metacestode (Abdominal cavity) | 14 | 0.28 | Cestoda: Dilepididae | ||
42 (84, 71 – 93) | Аdult (Gills) | 1 – 276 | 36.5 | Monogenea: Mazocraeidea | ||
12 (24, 13 – 38) | Third stage larva (Muscle) | 1 – 6 | 0.6 | Nematoda: Anisakidae |
The species composition of the fish was determined on the basis of a taxonomic descriptions according to Berg (1949), Kazancheyev (1981) and Reshetnikova (2002). A complete biological analysis of the fish was carried out with the determination of the length, mass, sex, maturity stages of the gonads (Pravdin 1966). The age of the fish were determined by rings on the scales or otoliths or by cuts of the marginal rays of the pectoral fins (Chugunova, 1959; Konoplev, 1975). The body length of all fish was measured from the top of the snout to the end of the scaly cover and to the end of the caudal fin. Fish were weighed on an electronic scale with an accuracy of 1 g. For small fish (atherin and common sprat) this was with an accuracy of 0.1 g. Fulton’s condition index (F) was calculated for each fish as:
F = 100*W/L3
where W = the weight in grams and L is the length in cm (Nash and Valencia 2006)
In the field, a complete parasitological dissection of fish was carried out according to the standard classical method (Skrabin, 1928; Dogel, 1933; Bykhovskaya – Pavlovskaya, 1985). The results of the autopsies of the fish were recorded. These included the fish species, the place of investigation, sex, age, weight of the fish, and the number, species and localization of detected parasites.
With a complete parasitological study, fish muscles and all internal organs were examined under a KRUSSMSZ5000 stereomicro-scope with a range of 7 – 45x. Parasites were fixed in various fixatives: monogeneans, trematodes, cestodes, and parasitic crustaceans in 700 alcohol, and nematodes in Barbagallo fluid. For species identification, nematodes were placed in a solution of glycerol with water (1: 1) in order to clear them and then view the internal structure of helminths. This therefore enabled the taxonomic identification based on the morphological features of the parasites. To investigate any affects of parasitism on the fish, a multivariable generalised linear model was used to analyse the association of the intensity of infection of each individual fish with the Fulton’s condition index. A backward selection method was used with all variables included in the initial model with each non significant variable with a p >0.15 being removed sequentially, with only significant variables remaining in the final model. In addition and associations in the intensity of infection with individual parasites were analysed. All analyses were undertaken in R (R Core Team, 2019).
For this study formal consent is not required.
A total of 656 fish belonging to 13 different species representing 6 orders were examined. In the present study 25 species of parasites were identified. These included 5 species of nematode, 8 species of trematodes, 6 monogean species, 2 cestode and 2 crustacea. In addition one unidentified species of nematode was recovered and one molusc. The number of fish infected with each parasite identified; abundance and range of intensity of infection; prevalence; developmental stage of the parasite recovered, and the organ of the fish from which the parasite was recovered are presented in Tables 1 – 5. Figures 2 – 6 illustrate some of the parasites recovered during this study.
There were 2 fish species from the order Clupeiformes and 4 different parasite species were found infecting these fish. These included 2 nematode one cestode and 1 Trematode species. Details are given in Table 1.
There were 3 fish species from the order Perciformes and 11 different parasite species were found infecting these fish. These included 2 nematode, 7 monogenean and 1 crustacean species (Table 2)
There were 5 fish species from the order Cypriniformes and 14 different parasite species were found infecting these fish. These included 2 nematode, 11 monogenean and 1 cestode species.
The number of fish infected and range of intensity of infection of parasites in fish of order Perciformes.
Fish host | Parasite | Number infected (prevalence, confidence intervals) | Development stage of parasite recovered | Range of intensity | Mean abundance | Parasite Taxon |
---|---|---|---|---|---|---|
42(84,71-93) | Third stage larva | 7-161 | 27.0 | Nematoda: Anisakidae | ||
9(18,9-31) | Third stage larva | 7-121 | 6.8 | Nematoda: Anisakidae | ||
6(12,5-24) | Adult | 1-17 | 0.62 | Monogenea: Ancyrocephalidae | ||
Creplin, 1839 | (Gills) | |||||
10(20,10-33) | Metacercaria | 2-20 | 1.46 | Trematoda: Diplostomidae | ||
Rudolphi, 1819 | (Eyes) | |||||
2(4,0.5-14) | Adult | 2-5 | 0.14 | Monogeneas: Gyrodactylidae | ||
1957 | (Gills) | |||||
2(4,0.5-14) | Metacercaria | 1-4 | 0.1 | Trematoda: Diplostomidae | ||
1850 | (Eyes) | |||||
17(34,21-49 | Adult | 1-19 | 1.72 | Crustacea: Ergasilidae | ||
1940 | (Gills) | |||||
6(12,5-24) | Third stage larva | 1-12 | 0.4 | Nematoda: Anisakidae | ||
2(4,0.5-14) | Adult | 14-29 | 0.86 | Monogeneas: Gyrodactylidae | ||
1962 | (Gills, skin) | |||||
2(4,0.5-14) | Adult | 2 | 0.04 | Crustacea: Ergasilidae | ||
1993 | (Gills) | |||||
27 (54, 39 - 68) | Third stage larva | 1-19 | 3.0 | Nematoda: Anisakidae | ||
(Abdominal cavity, muscle, serous membrane) | ||||||
3(6,1.3-17) | Metacercaria | 6-42 | 1.2 | Trematoda: Diplostomidae | ||
1(2,0.1-11) | Metacercaria | 4 | 0.08 | Trematoda: Diplostomidae | ||
19(38,25-53) | Metacercaria (Eyes) | 2-64 | 4.36 | Trematoda: Diplostomidae | ||
8(16,7-29) | Metacercaria | 2-8 | 0.64 | Trematoda: Diplostomidae |
The number of fish infected and range of intensity of infection of parasites in fish of order Mugiliformes.
Fish host | Parasite | Number infected (prevalence, confidence intervals) | Development stage of parasite recovered | Range of intensity | Mean abundance | Parasite Taxon |
---|---|---|---|---|---|---|
9 (18, 8.6 – 31) | Аdult (Gills) | 1 – 8 | 0.56 | Monogenea: Ancyrocephalidae | ||
1 (2, 0.1 – 11) | Metacercaria (Еyes) | 10 | 0.2 | Trematoda: Diplostomidae | ||
1 (2, 0.1 – 11) | Аdult (Gills) | 1 | 0.02 | Crustacea: Ergasilidae |
There was also 1 further unidentified nematode species (Table 4).
There was no association between Fulton’s condition index and the intensity of parasite infection for any of the fish species. For
This study aimed to identify important parasitic pathogens and zoonoses of fish from the Kazakhstan sector of the Caspian Sea and associated river basin. The fish studied also represent important species for commercial fisheries in this region and therefore this information makes a contribution to understanding parasitic diseases that may affect such stocks.
The number of fish infected and range of intensity of infection of parasites in fish of order Cypriniformes
Fish host | Parasite | Number infected (prevalence, confidence intervals) | Development stage of parasite recovered | Range of intensity | Mean abundance | Parasite Taxon |
---|---|---|---|---|---|---|
1(2,0.1-11) | Third stage larva | 1 | Nematoda: Anisakidae | |||
15(20,18-45) | (Abdominal cavity) Metacercaria (Eyes) | 2-14 | 1.7 | Trematoda: Diplostomidae | ||
25(50,36-64) | Metacercaria (Eyes) | 1-39 | Trematoda: Diplostomidae | |||
3(6,1.3-17) | Metacercaria (Eyes) | 3-6 | Trematoda: Diplostomidae | |||
2(4,0.5-14) | Adult (Gills) | 1 | Monogenea: Dactylogyridae | |||
1 (2,0.1-11) | Adult (Intestines) | 6 | Cestoda:Bothriocephalidae | |||
42 (84, 71 - 93) | Third stage larva (Abdominal cavity, muscle, serous membrane) | 3-1197 | Nematoda: Anisakidae | |||
13(26,15-40) | Third stage larva (Abdominal cavity, serous membrane) | 12-356 | Nematoda: Ascaridoidea | |||
2(4,0.5-14) | Metacercaria (Eyes) | 6-10 | Trematoda: Diplostomidae | |||
1 (2,0.1-11) | Metacercaria (Eyes) | 6 | Trematoda: Diplostomidae | |||
5(10,3.3-22) | Metacercaria (Eyes) | 2-6 | Trematoda: Diplostomidae | |||
24(48,34-63) | Metacercaria (Eyes) | 2-20 | Trematoda: Diplostomidae | |||
2(4,0.5-14) | Adult (Gills) | 3-8 | Trematoda: Diplostomidae | |||
1 (2,0.1-11) | Metacercaria (Eyes) | 7 | Trematoda: Diplostomidae | |||
2(4,0.5-14) | Metacercaria (Eyes) | 3-4 | Trematoda: Diplostomidae | |||
1 (2,0.1-11) | Adult (Gills) | 1 | Crustacea: Ergasilidae | |||
2(4,0.5-14) | Adult (Gills) | 4-18 | Monogenea: Dactylogyridae | |||
2(4,0.5-14) 2(4,0.5-14) | Metacercaria (Eyes) Metacercaria (Eyes) | 2-8 2-4 | 0.2 0.12 | Trematoda: Diplostomidae Trematoda: Diplostomidae | ||
66(12,5-24) | Metacercaria (Eyes) | 2-12 | 0.64 | Trematoda: Diplostomidae | ||
1 (2,0.1-11) | Metacercaria (Eyes) | 3 | 0.06 | Trematoda: Diplostomidae | ||
3(6,1.3-17) | Metacercaria (Eyes) | 6-12 | 0.48 | Trematoda: Diplostomidae | ||
19(38,25-53) | Metacercaria (Eyes) | 4-18 | 2.24 | Trematoda: Diplostomidae | ||
5(10,3.3-22) | Metacercaria | 2-4 | 0.32 | Trematoda: Diplostomidae | ||
5(10,3.3-22) | Adult (Gills) | 2-3 | 0.26 | Monogenea:Gyrodactylidae | ||
6(12,5-24) | Metacercaria (Eyes) | 2-36 | 1.28 | Trematoda: Diplostomidae | ||
7(14,5.8-27) 9(18,8.6-31) | Glochidium (larva) (Gills) - | 1-13 1-4 | 0.5 0.4 | Bivalvia: Unionidae Nematoda: | ||
3(6,1.3-17) | Adult (Intestines) | 1-2 | 0.08 | Nematoda: Camallanidae |
The number of fish infected and range of intensity of infection of parasites in fish of order Siluriformes.
Fish host | Parasite | Number infected (prevalence, confidence intervals) | Development stage of parasite recovered | Range of intensity | Mean abundance | Parasite Taxon |
---|---|---|---|---|---|---|
4 (67, 22 - 96) | Third stage larva (Abdominal cavity) | 12-563 | 114.3 | Nematoda: Anisakidae | ||
2(33,4.3-78) | Third stage larva (Abdominal cavity, serous membrane) | 72-254 | 54.33 | Nematoda: Dioctophymatidae | ||
1(17,0.4-64) | Metacercaria (Eyes) | 4 | 0.67 | Trematoda: Diplostomidae | ||
2(33,4.3-78) | Adult (Gills) | 4-6 | 1.67 | Monogenea:Ancyrocephalidae |
The zander is a species of fish from freshwater and brackish habitats in western Eurasia.
No previous information was found on the parasites of
The golden grey mullet (
Six species of helminths were found in the bream (
The carp (
Five species of parasites were found in silver crucian car
We have described 9 helminth species parasitizing the Asp (
We were not able to identify the parasites we recovered from
There was no relationship between Fulton’s condition score and the intensity of parasitic infection. This may indicate that the parasites have a low pathogenicity for the fish species investigated or that the intensity of infection was insufficient to cause any effects in the fish. We did find an increase in Fulton’s condition score with age in Carp and the Caspian Roach indicating an improvement in condition as the fish mature. Male zander were significantly more intensely infected with trematodes compared to females which may indicate a gender associated increased susceptibilities to infection or gender associated behavior resulting in an increased parasite burden. The associated between intensity of infection with monogeans and nematode larvae could be consistent with certain individuals having increased susceptibility to polyparasitsim or a statistical error as the p values was 0.04.
In summary this study has identified parasite species across 13 fish species that are endemic to the north Caspian Sea and drainage basin. A high proportion of the fish are infected with parasites of a zoonotic potential and therefore appropriate controls in the food chain should be considered to prevent human infection.