Effect of Dactylogyrus catlaius (Jain 1961) infection in Labeo rohita (Hamilton 1822): Innate immune responses and expression profile of some immune related genes.

The monogenean ectoparasite, Dactylogyrus sp. is a major pathogen in freshwater aquaculture. The immune responses in parasitized fish were analyzed by quantitation of innate immune factors (natural agglutinin level, haemolysin titre, antiprotease, lysozyme and myeloperoxidase activities) in serum and immune-relevant gene expression in gill and anterior kidney. The antiprotease activity and natural agglutinin level were found to be significantly higher and lysozyme activity was significantly lower in parasitized fish. Most of the genes viz., β2-microglobulin (β2M), major histocompatibility complex I (MHCI), MHCII, tumor necrosis factor α (TNFα) and toll-like receptor 22 (TLR22) in gill samples were significantly down-regulated in the experimental group. In the anterior kidney, the expression of superoxide dismutase and interleukin 1β (IL1β) were significantly up-regulated whereas a significant down regulation of MHCII and TNFα was also observed. The down-regulation of most of the genes viz, MHCI, β2M, MHCII, TLR22 and TNFα in infected gills indicated a well evolved mechanism in this parasite to escape the host immune response. The modulation of innate and adaptive immunity by this parasite can be further explored to understand host susceptibility.

Distribution and Abundance of Opisthorchis viverrini Metacercariae in Cyprinid Fish in Northeastern Thailand

To increase public health awareness for prevention of opisthorchiasis caused by eating raw freshwater fish, the distribution and abundance of Opisthorchis viverrini metacercariae (OV MC) was investigated in freshwater fish obtained from 20 provinces in northeastern Thailand between April 2011 and February 2012. A cross-sectional survey was conducted on 12,890 fish consisting of 13 species randomly caught from 26 rivers, 10 dams, and 38 ponds/lakes. Fish, were collected in each of the rainy and winter seasons from each province. Fish were identified, counted, weighed, and digested using pepsin-HCl. Samples were examined for OV MC by a sedimentation method, and metacercariae were identified under a stereomicroscope. OV MC were found in 6 species of fish; i.e., Cyclocheilichthys armatus, Puntius orphoides, Hampala dispar, Henicorhynchus siamensis, Osteochilus hasselti, and Puntioplites proctozysron from localities in 13 provinces. Among the sites where OV MC-infected fish were found, 70.0% were dams, 23.7% were ponds/lakes, and 7.7% were rivers. The mean intensity of OV MC ranged from 0.01 to 6.5 cysts per fish (or 1.3-287.5 cysts per kg of fish). A high mean intensity of OV MC per fish (>3 cysts) was found in 5 provinces: Amnat Charoen (6.5 cysts), Nakhon Phanom (4.3), Mukdahan (4.1), Khon Kaen, (3.5) and Si Sa Ket (3.4). In conclusion, OV MC are prevalent in natural cyprinid fish, with the infection rate varying according to fish species and habitats.

[Pathological study of neoechinorhynchus sp. [van cleave, 1919] in gastrointestinal tract of barbus sp. from the Zarrine-roud river, Iran]

All helminthes belonging to the phylum Acantocephala are obligatory parasites which are reported to be found in the gastrointestinal tract of definitive hosts such as fish worldwide and in Iran as well. The purpose of this study was undertaken to determine the frequency and pathological changes in the gastrointestinal tract of the Barbus sp. due to Neoechinorhynchus sp. over a one year period, 89 fish [Barbus sp.] were collected from the Zarine-Roud River. Intestines were removed and investigated for infection. Histopathological sections were prepared and stained in a routine manner using the Hematoxylin-Eosin [H and E] method. The prevalence of gastrointestinal infection with Neoechinorhynchussp. in Barbus sp. was 16%. Histopathological lesions were revealed epithelial thickness and folding. As a result of mechanical irritation, the Fibrinous enteritis with epithelial hyperplasia was developed. In the lamina properia and mucosa of the intestine, the vessels dilated and congested. Mucosa folding sections, hyperemia and inflammatory cell infiltration including eosinophile, lymphocyte and fibrinous were noted. It was concluded that Barbus fish infected by the Neoechinorhynchus species from the Zarine-Roud River, are not suitable for pond fish cultivation in the region and this can be cause for of severe economic losses

Holostephanus metorchis (Digenea: Cyathocotylidae) from Chicks Experimentally Infected with Metacercariae from a Fish, Pseudorasbora parva, in the Republic of Korea

Holostephanus metorchis (Digenea: Cyathocotylidae) is a patrrasite of birds, transmitted by freshwater fishes. H. metorchis adults were recovered from chicks experimentally infected with metacercariae collected from freshwater fishes, Pseudorasbora parva. The metacercariae were oval, surrounded with thick fibrous capsules. In adult flukes, the holdfast organ occupied the ventral concavity, and the anterior testis did not reach the level of the ventral sucker. Based on these morphological characteristics, these flukes were identified as H. metorchis.

High prevalence of Haplorchis taichui metacercariae in cyprinoid fish from Chiang Mai Province, Thailand.

This study aimed to investigate Haplorchis taichui metacercarial infection in fish collected from the Chom Thong and Mae Taeng districts, Chiang Mai Province during November 2001 to October 2002. A total 617 cyprinoid fish of 15 species were randomly collected and examined for H. taichui metacercariae. All the species of fish were found to be infected with H. taichui. The infection rates were 91.4% (266/290) and 83.8% (274/327), with mean intensities of 242.9 and 107.4 in the Chom Thong and Mae Taeng districts, respectively. The portion of the fish body with the highest metacercarial density was the muscles, and second, the head, in both districts. In addition, the fish had mixed-infection with other species of trematodes, namely: Centrocestus caninus, Haplorchoides sp, and Haplorchis pumilio.

A survey of helminths in cyprinoid fish from the Mae Ngad Somboonchon Reservoir, Chiang Mai Province, Thailand.

Five species of cyprinoid fish, Puntioplites proctozysron, Hampala macrolepidota, Labiobarbus siamensis, Barbodes gonionotus, and Henicorhynchus siamensis, were collected from Mae Ngad Somboonchon Reservoir, Chiang Mai Province from October 2002 to September 2003 and examined for parasites. Fourteen species of helminths were discovered: ten species of monogenea, Dactylogyrus macrolepidoti, D. protozysron, D. puntioplites, D. quadribrachiatus, Dactylogyrus sp I, II, III, Gyrodactylus sp, Paradiplozoon kamang, and P. krasoopensis; three species of metacercariae, Centrocestus caninus, Haplorchis taichui, and Haplorchoides sp and one species of nematode: Rhabdochona sp. The overall prevalence was 79.36% (373/470). The highest prevalence was found in Puntioplites proctozysron (90%, 81/90), and the lowest prevalence in Labiobarbus siamensis (60.64%, 57/94). Monogenea and metacercariae were found with the highest and lowest infection rates in the cool-dry and rainy seasons, respectively. Metacercariae of Centrocestus caninus and Haplorchis taichui are infectious to humans.

Clonorchis sinensis metacercarial infection in the pond smelt Hypomesus olidus and the minnow Zacco platypus collected from the Soyang and Daechung Lakes

The pond smelt Hypomesus olidus and minnow Zacco platypus were collected from the Soyang and Daechung Lakes in January 2003, and their metacercarial infections was examined by the muscle compression and artificial digestion techniques. In the Soyang Lake, 161 metacercariae of Clonorchis sinensis (0.35 per fish) were harvested from 459 pond smelts examined. Also, 13 metacercariae of C. sinensis (0.43 per fish), 1 of Metagonimus sp., 4 of Echinostoma sp., 148 of Centrocestus armatus and 44 unidentified species were collected from 30 minnows. In the Daechung Lake, 369 metacercariae of C. sinensis (3.69 per fish) and 51 unidentified species were recovered from 100 pond smelts. The metacercariae of C. sinensis were fed to experimental rats, in which the adult flukes were identified. The pond smelts and minnows collected from the Soyang and Daechung Lakes were verified to be the second intermediate hosts and the sources of human C. sinensis infection.

Population biology of Allocreadium lobatum Wallin, 1909 (Digenea: Allocreadiidae) in the creek chub, Semotilus atromaculatus, mitchill (Osteichthyes: Cyprinadae), in a Nebraska Creek, USA

Allocreadium lobatum Wallin, 1909 has been reported in cyprinid species of freshwater fish in Canada and in the United States. The population biology of A. lobatum in the host Semotilus atromaculatus Mitchill was studied from May through December 1991, in a USA creek. Overall prevalence (64 percent) and mean intensity (4.4 + or - 0.4) were greater than previously reported while abundance, reported for the first time, was 2.8 + or - 0.3. Several trends in A. lobatum population biology as a function of S. atromaculatus length were identified. Mean intensity and abundance of A. lobatum increased with host size and significant differences in prevalence and A. lobatum lengths were found to correlate with host lengths

In vitro excystation of Haplorchis taichui (Trematoda: Heterophyidae).

The effects of trypsin, bile extract, temperature and acid-based condition for the in vitro excystation of Haplorchis taichui metacercariae were studied. At 37 degrees C, approximately half the number of metacercariae excysted when exposed to 1% trypsin for 15 minutes with no more excystation found beyond this time. Increasing trypsin concentration seemed to reduce the excystation rate while bile extract was, however, unlikely to be an absolute requirement. A temperature of 37 degrees-41 degrees C yielded a similar excystation result in combination with 1% trypsin; however, less excystation occurred at a lower temperature of 35 degrees C. The acid-based environment of pH 8 gave the best excystation result in association with 1% trypsin at a temperature of 39 degrees C. Higher and lower basicity produced a smaller excystation rate. An environmental condition of 1% trypsin at pH 8 and a temperature of between 37 degrees-41 degrees C was recommended for the in vitro excystation of H. taichui metacercariae. The relatively broad temperature and pH range condition for the excystation of H. taichui corresponded with various definitive hosts that were infected naturally by this fluke.

In vitro development of Haplorchis taichui (Trematoda: Heterophyidae).

Newly excysted metacercariae of Haplorchis taichui were cultured in a candle jar set at 37 degrees C. Both monophasic culture media [0.85% NaCl, RPMI 1640, RPMI 1640+10% fetal calf serum (FCS)] and diphasic culture media [RPMI 1640 + egg yolk agar, RPMI 1640 + 5%, 10% or 15% blood in blood agar (BA), RMPI 1640 + 5%, 10% and 15% FCS with 5% blood in BA] were used in vitro. Parasites survived for only 1 day in 0.85% NaCl without any development. In RPMI 1640 with egg yolk agar and RMPI 1640 + 5%, 10% FCS, the parasite survived for 3-5 days. In contrast, worms survived for 12-14 days in RPMI 1640 with blood agar without any change in result in a different concentration of blood in BA. The ovary and testes were observed after 3 days incubation in this media. Nevertheless, only 1 parasite in RPMI 1640 with 15% blood in BA had vitellaria and eggs at day 6. RPMI 1640 with blood agar can be used as short-term maintenance for the in vitro culture of H. taichui. However, further studies are needed.

Intensity of trematode metacercariae in cyprinoid fish in Chiang Mal Province, northern Thailand.

The intensity of infection of trematode metacercariae was determined in five species of cyprinoid fish collected from Mae Ngud reservoir, Chiang Mai Province. These species were Thynnichthys thynnoides, Puntioplites proctozysron, Hampala macrolepidota, Puntius leiacanthus and Puntius gonionotus. T. thynnoides contained the highest number (83.0%) of metacercariae, whereas P. gonionotus had the fewest (0.19%). The caudal fin was the area of highest infection of metacercariae (49.39%), with the anal fin having the fewest (5.93%). Most metacercariae was isolated from Haplorchis taichui (63.27%), with an intensity variation of 0.3-165.2 metacercariae/fish.

Surface ultrastructure of excysted metacercariae of Haplorchis taichui (Trematoda: Heterophyidae).

The morphology of newly excysted juvenile Haplorchis taichui was studied using a light and a scanning electron microscope (SEM). The reproductive organs were well developed. The whole body surface was covered with numerous transverse rows of scale-like spines, which had 3-11 points at the tip. The spines on the dorsal were similar with those on the ventral surfaces in shape, size and number of points. The spines in anterior were digitated into 10-11 points, then 8-9 points and 7 points. The presence of 3 points in each spine was observed in the area adjacent to the excretory pore. Two types of sensory papillae existed throughout the body: type I, ciliated knob-like swellings and type II, round swellings of the tegument. The rapid maturation of H. taichui results from the development of both internal and external organs during the newly excysted stage.

Opisthorchis viverrini metacercaria in Thai freshwater fish.

Examination for metacercaria in freshwater fish, the common intermediate hosts of Opisthorchis viverrini was carried out during 1992-1996. The 4-year survey of fish from markets in 14 provinces revealed that metacercariae of O. viverrini were found in fish from Udon Thani, Sa Kaeo and Prachin Buri Provinces; fish from Aranyaprathet district had the highest positive rates (25-28%). Fish from 12 provinces were found to be positive with heterophyid metacercariae, namely: Haplorchis pumilio, H. taichui, H. yokogawai, Stellantchasmus falcatus, Centrocestus formosanus and Haplorchoides cahirinus. It was also observed that the prevalence of O. viverrini metacercaria in fish decreased markedly during the last 10 years.

Common culture practices for cyprinids in Asia.

Cyprinids are the largest group of cultured freshwater fish and thus the most important from the aspect of fish-borne parasitic zoonoses. The common practices employed in the culture of this group are described to provide background information which may be used in the formulation of strategies for the control of these zoonoses. Only the common carp is cultured in monoculture: all the rest of the carp species are usually cultured in polyculture systems incorporating several species. Polyculture of cyprinids may be carried out in ponds, cages or in free range culture in natural or man-made water bodies, Polyculture of cyprinids is often integrated with agriculture, such as livestock, poultry or crop farming, utilizing byproducts of the agriculture activity, especially manure, as a source of nutrient for the fish pond. If precautions are not taken, this practice may provide an avenue for the transmission of fish borne parasites to man.

Current status of food-borne parasitic zoonoses in Laos.

Stool samples from a total of 1,008 persons were examined for intestinal parasites during a comprehensive study on the epidemiology of small fluke infections in Laos. The prevalence of small fluke eggs in the stool was seen to peak at age 20 years, particularly in men from villages (90.4%). Three quarters of infections belong to the category of light infections and only 0.6% to the category of very heavy according to eggs per gram of feces (EPG). The highest EPG was in the 11-15 year age group. In addition, the following parasites were diagnosed: Sarcocystis hominis (prevalence more than 10% in the group over 20 years of age), Taenia sp. (12.4% for the village people over 20 years), Fasciolopsts buski (3.8% for the same group). The habit of Laos people to eat raw fish, beef and pork flesh, is reflected in significant epidemiological consequences. Cercariae of Opisthorchis viverrini occurred in 0.5% of Bithynia siamensis goniomphalus examined, Haplorchis sp. cercariae were found in 0.9% of Tarebia granifera snails. Metacercariae of O. viverrini were found in flesh of 7 species of cyprinid fish. Haplorchis taichui in 4 species of these fish, and H. pumilio of two cyprinid species. Hampala macrolepidota harbored larvae of all above mentioned species. Stellantchasmus falcatus was recovered in fins of belonid fish Xenentodon cancila. Adults of O. viverrini were found in 36% of domestic and stray cats, Heterophyid flukes were found in 24% cats. The most frequent species were H. taichui and H. yokogawai. Eight Laotian students were treated in Czechoslovakia with praziquantel to determine fluke infection. Three were infected only by O. viverrini, four only by H. taichui and one by both O. viverrini and H. taichui. These results demonstrate the problem of correct differential diagnosis of food-borne small fluke infections and the need to assess the clinical course and public health aspects of infections.

Opisthorchis viverrini : intensity and rates of infection in cyprinoid fish from an endemic focus in Northeast Thailand.

The infection rates and monthly variations in intensities of Opisthorchis viverrini infection in cyprinoid fish from an endemic focus in Northeast Thailand were investigated between April 1980 and March 1981. Out of six species of cyprinoid fish examined, four were found to harbour O. viverrini metacercariae. All four species of infected fish showed high rates of infection. Among the four species of O. viverrini infected fish, Cycloccheilicthys apagon and Puntius leiacanthus were found in abundance. The results indicate very little variation in the rates of infection throughout the year. On the other hand, intensities of infection varied from month to month, ranging from 8 to 88 metacercariae per fish for C. apagon and from 8 to 32 metacercariae per fish for P. leiacanthus. O. viverrini metacercariae were found in the fish muscle throughout the body; however, the body muscle harboured the highest density of metacercariae, followed by the dorsal fin, pectoral fin, pelvic fin and anal fin muscles respectively. In lieu of all these findings, it is therefore invalid to assume as indicated by the former workers that any potential intermediate fish host that does not have the O. viverrini metacercariae in its pectoral fin muscle in negative with opisthorchiasis.