Description and prevalence of gregarines infecting the amphipod Gammarus pulex, in the Water of Leith, Scotland, UK.

Gregarines are symbiotic protists that are found in a broad spectrum of invertebrates, including insects, crustaceans, and annelids. Among these the globally distributed amphipod Gammarus pulex is one of the earliest recognized hosts for aquatic gregarines and is prevalent among macroinvertebrates in freshwater environments. In this study, samples of G. pulex were collected in the Water of Leith river, Scotland, UK. Gregarines were identified using light and scanning electron microscopy as well as standard molecular techniques. We identified three septate eugregarine symbionts-Heliospora longissima, Cephaloidophora gammari, and the here newly characterized Cephaloidophora conus n. sp. (formerly Cephaloidophora sp.) associated with Gammarus pulex in the Water of Leith. Prevalences for identified gregarine species were calculated and seasonal dynamics of gregarine infections/colonization were analyzed. Prevalences were highest in autumn and spring reaching almost 50 %. While the two Cephaloidophora species showed similar colonization patterns, the prevalence of Heliospora showed an opposite trend. Identifying gregarine infection/colonization patterns is one step towards better understanding the gregarine-host relationship, as well as possible impacts of the gregarines on their hosts.

Gastrointestinal and ectoparasites from urban stray dogs in Fortaleza (Brazil): high infection risk for humans?

Dogs are important definite or reservoir hosts for zoonotic parasites. However, only few studies on the prevalence of intestinal parasites in urban areas in Brazil are available. We performed a comprehensive study on parasites of stray dogs in a Brazilian metropolitan area. We included 46 stray dogs caught in the urban areas of Fortaleza (northeast Brazil). After euthanization, dogs were autopsied. Ectoparasites were collected, and the intestinal content of dogs were examined for the presence of parasites. Faecal samples were collected and analysed using merthiolate iodine formaldehyde concentration method. A total of nine different parasite species were found, including five endoparasite (one protozoan, one cestode and three nematode species) and four ectoparasite species (two flea, one louse and one tick species). In the intestinal content, 3,162 specimens of four helminth species were found: Ancylostoma caninum (prevalence, 95.7%), Dipylidium caninum (45.7%), Toxocara canis (8.7%) and Trichuris vulpis (4.3%). A total of 394 ectoparasite specimens were identified, including Rhipicephalus sanguineus (prevalence, 100.0%), Heterodoxus spiniger (67.4%), Ctenocephalides canis (39.1%) and Ctenocephalides felis (17.4%). In the faeces, intestinal parasites were detected in 38 stray dogs (82.6%), including oocysts of Giardia sp. (2.2%) and eggs of the nematode A. caninum (82.6%). Neither eggs nor larval stages of D. caninum, T. canis or T. vulpis were detected in dog faeces. Sensitivity of faecal examination for A. caninum was 86.4% (95% confidence interval, 72.0-94.3) but zero percentage for the other intestinal helminth species. Our data show that stray dogs in northeast Brazil carry a multitude of zoonotic ecto- and endoparasites, posing a considerable risk for humans. With the exception of A. caninum, sensitivity of faecal examination was negligible.

Transmission of fish parasites into grouper mariculture (Serranidae: Epinephelus coioides (Hamilton, 1822)) in Lampung Bay, Indonesia.

Differently fed groupers Epinephelus coioides from an Indonesian finfish mariculture farm were studied for ecto- and endohelminth parasites. Pellet-fed E. coioides were infested with 13 parasite species/taxa of which six had a monoxenous and seven a heteroxenous life cycle. A total of 14 parasite species/taxa were found in the fish that were fed with different trash fish species, four of them with a monoxenous and ten with a heteroxenous life cycle. The use of pellet food significantly reduced the transfer of endohelminths and the number of parasites with a heteroxenous life cycle. Out of ten studied trash fish species, 62 parasite species were isolated (39% ectoparasitic and 61% endoparasitic), four of them also occurring in the cultured E. coioides and 14 in different groupers from Balai Budidaya Laut Lampung. The trash fish is held responsible for the transmission of these parasites into the mariculture fish. Endohelminth infestation of pellet fed fish demonstrates that parasite transfer also occurs via organisms that naturally live in, on, and in the surroundings of the net cages. Seventeen recorded invertebrates from the net cages might play an important role as intermediate hosts and hence parasite transmitters. The risk of parasite transfer can be considerably reduced by feeding selected trash fish species with a lower parasite burden, using only trash fish musculature or minimizing the abundance of invertebrates (fouling) on the net cages. These methods can control the endoparasite burden of cultivated fish without medication. The control of ectoparasites requires more elaborate techniques. Once they have succeeded in entering a mariculture farm, it is almost impossible to eliminate them from the system.

Genetic variability in Hysterothylacium aduncum, a raphidascarid nematode isolated from sprat (Sprattus sprattus) of different geographical areas of the northeastern Atlantic.

Species of the genus Hysterothylacium are among the most common marine nematode fish parasites in the northern Atlantic. Due to recent findings of cryptic speciation in other parasitic ascaridoid nematodes, a similar pattern of sibling species was hypothesized also for Hysterothylacium aduncum. By investigating a 886- to 890-bp-long genomic DNA fragment including ITS-1, 5.8S rDNA and ITS-2 of 40 specimens of H. aduncum of sprat (Sprattus sprattus) of four different biogeographical regions (North Sea, English Channel, Bay of Biscay, Adriatic Sea), we could not detect significant genetic variability and therefore cryptic speciation. Nevertheless, while ITS-1 and 5.8S rDNA sequences were identical for all analysed specimens, ITS-2 sequences showed a population-specific pattern with the differentiation of an English Channel/Bay of Biscay group from a North Sea/Mediterranean Sea group.

Parasite fauna of bream Abramis brama and roach Rutilus rutilus from a man-made waterway and a freshwater habitat in northern Germany.

Fifty specimens each of bream Abramis brama and roach Rutilus rutilus were examined for metazoan parasite fauna and trichodinid ciliates; 25 specimens of each species were collected from the Kiel Canal, a man-made waterway, and a nearby freshwater lake, the Dieksee. This is the first detailed parasitological examination of A. brama and R. rutilus at these locations: 30 parasite species were found, comprising 4 protozoans, 4 myxozoans, 5 digeneans, 3 monogeneans, 2 cestodes, 6 nematodes, 2 acanthocephalans, 3 crustaceans and 1 hirudinean. The crustacean Caligus lacustris occurred in both habitats while 2 other crustacean species, 2 acanthocephalans and 1 hirudinean were recorded exclusively for the lake habitat. Larval as well as adult stages of the different parasite species were found, indicating that both fish species act as intermediate and final hosts in both habitats. The Kiel Canal (total of 17 parasite species) showed a lower parasite species richness for A. brama and R. rutilus (14 and 10 parasite species, respectively) than the lake (25 parasite species). A. brama had a higher parasite richness (22 species) than R. rutilus (16 species) in the lake habitat. Most parasites collected were of freshwater origin. Consequently, the observed infection pattern of both fish species in the waterway is mainly influenced by the limited salinity tolerance of freshwater parasites, which are negatively affected even by a salinity of 2.3 to 4.5. In the central Kiel Canal, neither fish species was infected with marine parasites of low host specifity. These parasites are either limited by the low salinity at this sampling site (<4.5 to 6.0) or they cannot enter the canal due to the environmental conditions prevailing in this artificial brackish water habitat. Thus, the canal may comprise a natural barrier preventing the distribution of North Sea parasites into the Baltic Sea. However, the brackish water Baltic Sea nematodes Paracuaria adunca and Cosmocephalus obvelatus were found in R. rutilus from the canal, demonstrating the ability of some parasite species to invade and extend their range of distribution through this man-made shipping route from the Baltic to the North Sea.

Life cycle strategy of Hysterothylacium aduncum to become the most abundant anisakid fish nematode in the North Sea.

The present study demonstrates the influence of physical systems (mixed and stratified waters) on the occurrence and distribution of the anisakid nematode Hysterothylacium aduncum in commercially important gadiform fish species from the central and northern North Sea. Stratified waters are essential in structuring marine food webs and are therefore also important for the transfer of fish parasites to their host species. During two research cruises in 2001, 308 haddocks (Melanogrammus aeglefinus) and 203 whitings (Merlangius merlangus) were caught in the central and northern North Sea and were examined for anisakid nematode parasites and food composition. Additionally, the most abundant pelagic invertebrates, hyperiid amphipods, of the investigated area were sampled and examined with regard to their parasite infestation rates. The influence of stratified waters on the infestation of the gadiform fish species by H. aduncum was shown by ecological and parasitological investigations. In stratified areas haddocks and whitings feed specifically and invariably on pelagic hyperiids. The number of ingested hyperiids in these areas was in both fish species correlated with infestation rates of H. aduncum. Therefore, hyperiids were identified as the obligatory intermediated host of H. aduncum, since these crustaceans carried high numbers of nematode larvae in their haemocoel. The results of the present study demonstrate that haddocks and whitings from the stratified waters are highly parasitised, both in terms of the numbers of individuals of larval and adult stages of H. aduncum.

The life cycle of Anisakis simplex in the Norwegian Deep (northern North Sea).

Copepoda (Calanus finmarchicus n = 1,722, Paraeuchaeta norvegica n = 1,955), Hyperiidae (n = 3,019), Euphausiacea (Meganyctiphanes norvegica n = 4,780), and the fishes Maurolicus muelleri (n = 500) and Pollachius virens (n = 33) were collected in the Norwegian Deep (northern North Sea) during summer 2001 to examine the importance of pelagic invertebrates and vertebrates as hosts of Anisakis simplex and their roles in the transfer of this nematode to its final hosts (Cetaceans). Third stage larvae (L3) of A. simplex were found in P. norvegica, M. muelleri and P. virens. The prevalence of A. simplex in dissected P. norvegica was 0.26%, with an intensity of 1. Prevalences in M. muelleri and P. virens were 49.6% and 100.0%, with mean intensities of 1.1-2.6 (total fish length >or=6.0-7.2) and 193.6, respectively. All specimens of C. finmarchicus and M. norvegica examined were free of anisakid nematode species and no other parasites were detected. P. norvegica, which harboured the third stage larvae, is the obligatory first intermediate host of A. simplex in the investigated area. Though there was no apparent development of larvae in M. muelleri, this fish can be considered as the obligatory second intermediate host of A. simplex in the Norwegian Deep. However, it is unlikely that the larva from P. norvegica can be successfully transmitted into the cetacean or pinniped final hosts, where they reach the adult stage. An additional growth phase and a second intermediate host is the next phase in the life cycle. Larger predators such as P. virens serve as paratenic hosts, accumulating the already infective stage from M. muelleri. The oceanic life cycle of A. simplex in the Norwegian Deep is very different in terms of hosts and proposed life cycle patterns of A. simplex from other regions, involving only a few intermediate hosts. In contrast to earlier suggestions, euphausiids have no importance at all for the successful transmission of A. simplex in the Norwegian Deep. This demonstrates that this nematode is able to select definite host species depending on the locality, apparently having a very low level of host specificity. This could explain the wide range of different hosts that have been recorded for this species, and can be seen as the reason for the success of this parasite in reaching its marine mammal final hosts in an oceanic environment.