Wide Range Of Intermediate Hosts Research Articles

Molecular identification of Sarcocystis neurona in tissues of wild boars (Sus scrofa) in the border region between Brazil and Uruguay.

Sarcocystis neurona, owing to its clinical importance in domestic animals, is currently one of the most studied agents, presenting a wide range of intermediate hosts that have not yet been described, mainly in wild fauna. Thus, the aim of this study was to describe the detection and molecular detection of S. neurona by amplification of the 18S rRNA region in the tissues of wild boars killed by boar control program in border Brazil Uruguay. A total of 79 samples of DNA from wild boar tissues from the LADOPAR/UFSM sampling bank were used, with Nested-PCR reactions being performed for amplification of the 18S rRNA region and the expected final product of 290bp. Subsequently, the positive samples were subjected to restriction fragment length polymorphism (RFLP) technique with the restriction enzymes DdeI and HPAII. A second semi-Nested reaction was performed to obtain a larger sequence of nucleotides with amplification of the 18S region and the expected final product of 500bp for S. neurona and Nested amplification ITS1 with product final of 367 pb. In 32 samples, it was possible to detect S. neurona both by nested Nested-PCR reaction and RFLP, and the presence of the agent was confirmed by sequencing, corresponding to 40.51% of the total tissues evaluated. This is the first report of the occurrence of this species of Sarcocystis in wild boars, and further studies evaluating the role of these animals as intermediate hosts, and in the epidemiology of this protozoan are necessary, as well as verifying the risk factors for infection.

Seroprevalence and risk factors of Toxoplasma gondii infection in slaughtered chickens in Tripoli, Lebanon.

Toxoplasma gondii is a cosmopolitan protozoan parasite that has a wide range of intermediate hosts. It infects all warm-blooded animals, including humans and birds. The latter typically pick up the infection by ground feeding, and people can contract the parasite from eating undercooked chicken meat. In recent years, investigations into T. gondii infection in poultry have been reported worldwide. However, there is no epidemiological data regarding the seroprevalence of anti-T. gondii antibodies in chicken in Lebanon. Thus, the current investigation was carried out to determine the seroprevalence and associated risk factors of T. gondii infection in chicken destined for human consumption in the Tripoli district of Lebanon. For this, a cross-sectional study was carried out between April 2021 and February 2022. Blood samples were collected from 400 chickens in four poultry abattoirs in Tripoli. The modified agglutination test (MAT) was used to test sera for T. gondii antibodies. The association of T. gondii seroprevalence with potential risk factors was assessed using the Chi-square test. Multivariate analysis was used to confirm the association. The seroprevalence of T. gondii antibodies reported in this study was 13% (52/400); it was higher in the free-range chicken group (19.3%, 29/150) than in the caged group (9.2%, 23/250) (OR=2.365; 95% CI: 1.311-4.267) (P=0.004). The wet season and the presence of cats in the poultry farms were significantly associated with an increased seropositivity to T. gondii infection (P≤0.0001). Given the occurrence of T. gondii antibodies in slaughtered chicken in this area, the consumption of raw or undercooked chicken meats may pose a serious threat to public health and highlight the need to implement appropriate precautionary strategies to halt the spread of T. gondii to humans.

Serotyping, a challenging approach for Toxoplasma gondii typing.

Genotype analysis has revealed a high genetic diversity in strains of Toxoplasma gondii, isolated from a wide range of intermediate hosts and different geographic origins. Diversity is notably striking for parasites from wild hosts in South America, generally referred as non-archetypal genotypes. Those genotypes are implicated in the etiology of severe clinical disease, multivisceral toxoplasmosis, associated with high rate of mortality in immunocompetent individuals. Can we accept specific antibodies produced during T. gondii infection as biomarkers to identify infecting genotypes? Scientific evidence supports a positive response to this question; however, the genetic diversity of T. gondii genotypes organized into 16 haplogroups and collectively defined in 6 major clades, provides a reminder of the complexity and difficulty for the purpose. This review discusses serological approaches to genotyping T. gondii.

The Dangerous Side of Being a Predator: Toxoplasma gondii and Neospora caninum in Birds of Prey.

Toxoplasma gondii and Neospora caninum are apicomplexan protozoa of major concern in livestock and T. gondii is also considered one of the major threats and a public health concern. These protozoa have a wide range of intermediate hosts, including birds. The present work aimed to assess the prevalence of these cyst-forming parasites in migratory and sedentary birds of prey. The skeletal muscle and myocardium of 159 birds of prey from Central Italy, belonging to 19 species and recovered across 6 Wildlife Recovery Centers/Care structures along the Italian migratory route, were collected specifically for molecular (PCR) and for histopathological analysis to detect T. gondii and N. caninum. For the molecular analysis, genomic DNA was extracted. The DNA was tested by sequence typing, targeting GRA6, 529 bp repeated element, B1, PK1, BTUB, SAG2, alt.SAG2, and APICO genes for T. gondii and to end-point PCR targeting NC5 gene for N. caninum. Thirty-seven out of the one hundred and fifty-nine analyzed samples tested positive for T. gondii with a prevalence of 23.27% and nine for N. caninum, with a prevalence of 5.66%. Thirty-two sequences were obtained from the thirty-seven isolates of T. gondii. Among these, 26 presented alleles compatible with type I strain in 1 or more loci, 4 with type II strain and 2 consisted of atypical strains. Toxoplasma gondii genetic variability in birds of prey confirms previous findings of wildlife as reservoirs of atypical strains. Results from the histology showed few protozoal tissue cysts in skeletal muscle (n. 4) and hearts (n. 2).

The genome of the thin-necked bladder worm Taenia hydatigena reveals evolutionary strategies for helminth survival

Taenia hydatigena is a widespread gastrointestinal helminth that causes significant health problems in livestock industry. This parasite can survive in a remarkably wide range of intermediate hosts and affects the transmission dynamics of zoonotic parasites. T. hydatigena is therefore of particular interest to researchers interested in studying zoonotic diseases and the evolutionary strategies of parasites. Herein we report a high-quality draft genome for this tapeworm, characterized by some hallmarks (e.g., expanded genome size, wide integrations of viral-like sequences and extensive alternative splicing during development), and specialized adaptations related to its parasitic fitness (e.g., adaptive evolutions for teguments and lipid metabolism). Importantly, in contrast with the evolutionarily close trematodes, which achieve gene diversification associated with immunosuppression by gene family expansions, in T. hydatigena and other cestodes, this is accomplished by alternative splicing and gene loss. This indicates that these two classes have evolved different mechanisms for survival. In addition, molecular targets for diagnosis and intervention were identified to facilitate the development of control interventions. Overall, this work uncovers new strategies by which helminths evolved to interact with their hosts.

Serosurvey of Toxoplasma gondii, Neospora caninum and Sarcocystis neurona in raptors and risk factor analysis

Raptors are carnivorous birds with great hunting ability. Toxoplasma gondii, Neospora caninum and Sarcocystis spp. are intracellular Apicomplexan protozoans which infect a wide range of intermediate hosts, including birds. The aims of this study were to evaluate the serological reactivity of captive raptors serum to T. gondii, N. caninum and S. neurona antigens and identify possible risk factors associated with the infection. From August 2014 to September 2015, blood samples from 72 raptors were collected and serum samples were tested by immunofluorescence antibody test (IFAT). Antigen slides were prepared using tachyzoites of T. gondii and N. caninum and using merozoites of S. neurona. Serum samples were tested at the following cut-off dilutions: 1:16 for T. gondii and 1:50 for N. caninum and S. neurona. An anti-chicken IgY antibody conjugated with FITC was used as a secondary antibody at 1:50 dilution. Out of the 72 raptors serum tested by IFAT, 2.7% reacted to N. caninum, 8.3% to T. gondii and 11.1% to S. neurona antigens. The region in which the sample was collected, the reason the raptors were kept in captivity and diet were statistically associated with seropositivity to T. gondii and the use of the birds and diet were statistically associated with seropositivity to N. caninum and S. neurona (p≤0.05). We highlight the occurrence of these protozoans in birds of prey and the importance of good hygiene and feeding management of these birds in captivity to reduce the risk of protozoal infections.

Diversity of Taenia and Hydatigera (Cestoda: Taeniidae) in domestic dogs in Kenya.

Taenia species of domestic dogs can cause cysticercosis and coenurosis in a wide range of intermediate hosts including humans. Most taeniids of dogs are globally distributed, but some wildlife-transmitted species can be specific for certain regions. Generally, little information exists on the species composition and frequency in most regions of the world, which impairs risk assessment and control strategies. This study determined the range of taeniid species in dogs in four widely spaced areas of Kenya by genetic identification of eggs in faeces collected from the environment. Individual taeniid eggs were characterised by nested polymerase chain reaction of NADH dehydrogenase subunit 1 and cytochrome C oxidase 1 genes, restriction fragment length polymorphism and partial sequencing. Overall 79/1621 (4.9%) faecal samples contained eggs of Taenia or Hydatigera (8.0% in Turkana, 4.8% in Isiolo, 3.8% in Maasai Mara and 1.3% in Meru). Taenia hydatigena and T. multiceps were the most frequent, found in 36 and 15 samples, respectively. Other eggs found in the faeces belonged to T. serialis (sensu lato), T. madoquae (the first record in domestic dogs), T. ovis, T. saginata and Hydatigera taeniaeformis. Polymorphism of nad1 sequences revealed 22 and 8 haplotypes of T. hydatigena and T. multiceps, respectively. The results show the involvement of dogs in both domestic and sylvatic transmission cycles. In addition to the species range, this study provides data on the intraspecific diversity of T. hydatigena and T. multiceps in Kenya, which will serve as baseline information for further studies into cysticercosis and coenurosis in livestock and humans in the region.

Updates on Ecology and Life Cycle of Sulcascaris sulcata (Nematoda: Anisakidae) in Mediterranean Grounds: Molecular Identification of Larvae Infecting Edible Scallops.

Sulcascaris sulcata is a nematode parasite of sea turtles, widespread in neritic foraging grounds with variable prevalence, reaching 30% in loggerhead turtles Caretta caretta feeding in northern Adriatic Sea. Ulcerative gastritis associated to high intensity of infection is reported in this host species. The life cycle of S. sulcata has been elucidated in Australian and American waters, demonstrating the ability of the species of infecting a wide range of intermediate hosts, represented by bivalve and gastropod molluscs. During regular sanitary inspections, nematode larvae were found within the adductor muscle of Pecten jacobeus and Aequipecten opercularis collected from the Northern Adriatic Sea. Morphological and molecular analyses were performed for the identification of larvae, and molecular data were obtained from adult S. sulcata as well. Analysis of the sequences of ITS fragment, and mitochondrial genes cox1 and cox2, revealed high genetic similarity among all the samples, and no geographical clustering was observed between adult parasites collected in Adriatic and Tyrrhenian Seas. A common allele pool was detected also between the two developmental stages, included larvae from Pecten and Aequipecten. The comparison with other members of the family Anisakidae demonstrated that S. sulcata formed a clear monophyletic cluster. This study reports the first identification of intermediate hosts for S. sulcata within the Mediterranean Sea. Infection in edible scallops justifies the exclusion of the product from the market and zoonotic potential of larvae of this anisakid nematode are yet to be completely excluded. Fidelity of sea turtles to selected foraging grounds, such as the Northern Adriatic shelf, warrants the life cycle of S. sulcata to perpetrate in the area; at the same time, long distance migrations of individuals justify the dispersal of infecting elements over the Mediterranean basin, regardless of turtles' origin.

GRA24-Based DNA Vaccine Prolongs Survival in Mice Challenged With a Virulent Toxoplasma gondii Strain.

Toxoplasma gondii causes infections in a wide range of intermediate hosts and remains a threatening disease worldwide because of the lack of effective drugs and vaccines. Dense granule protein 24 (GRA24) is a novel essential virulence factor that is transferred into the nucleus of host cells from the parasitophorous vacuole to regulate gene expression. In the present study, bioinformatic analysis showed that GRA24 had a high score for B-cell and T-cell epitopes compared with surface antigen 1 (SAG1), which has been studied as a promising vaccine candidate. As a DNA vaccine, pVAX1-GRA24 was injected intramuscularly into BALB/c mice and the induced immune response was evaluated. pVAX1-GRA24 induced high levels of a mixed Th1/Th2 cytokines at 6 weeks after immunization. Antibody determinations, cytokines [interferon gamma (IFN-γ), interleukin (IL)-12, IL-4, IL-10], antigen-specific lymphocyte proliferation, CD4+ and CD8+ T lymphocytes, and cytotoxic T lymphocyte activity showed that mice immunized with pVAX1-GRA24 produced specific humoral and cellular immune responses. The expression levels of interferon regulatory factor 8 (IRF8), nuclear factor kappa B (NF-κB), and T-Box 21 (T-bet) were significantly higher in the pVAX1-GRA24 immunization group than in the control groups. Survival times were prolonged significantly (24.6 ± 5.5 days) in the mice immunized with pVAX1-GRA24 compared with the mice in the control groups, which died within 7 days of T. gondii challenge (p < 0.05). The results of the present study showed that pVAX1-GRA24 induced a T. gondii-specific immune response and thus represents a promising candidate vaccine to treat toxoplasmosis.

Toxoplasma gondii infection in raptors from Italy: Seroepidemiology and risk factors analysis

Toxoplasma gondii is a zoonotic parasite infecting a wide range of intermediate hosts, including birds. Nevertheless, scant information on the spread of infection in wild bird populations is available to date. With the aim of updating information on T. gondii infection in birds of prey and possible risk factors associated with the infection, a serosurvey was planned on both wild and captive raptors. An overall of 93 raptors from Northern Italy were tested for the presence of anti-T. gondii antibodies with a commercial modified agglutination test (MAT). A T. gondii prevalence of 10.7% was recorded; the highest seroprevalence was observed within the Family Strigidae (12.5%). Only wild animals tested positive; any statistical difference among species, taxonomic family, age, origin, use, migratory behavior and diet composition was not highlighted. Toxoplasmosis in birds of prey, sentinel species for the environmental spread of T. gondii, should always be considered within sanitary programs devoted to avian species protection.

Prevalence and Molecular Characterization of Cysticercus tenuicollis Isolated from Some Intermediate Host in Kurdistan-Iraq

Cysticercus tenuicollis (C. tenuicollis) is the larval stage infection of Taenia hydatigena, a common tapeworm of dogs and other Canidae, which has a wide range of intermediate hosts including sheep, goat, cattle, deer, camel, horse, human and other wild ruminants, the disease spreads through a contaminated water, soil and food with feces of infected dogs or other carnivores, T. hydatigena lives in the intestinal of the definitive host (carnivores) and excretes a huge number of eggs with feces daily. The present study conducted to determine the prevalence rate and molecular characterization of C. tenuicollis among sheep and goats in Sulaimani province. A total of 14088 slaughtered animals were inspected postmortem from the new Sulaimani abattoir comprise, which involves 13395 sheep and 693 goats. The selected cysts were preserved in 70% Ethanol for DNA extraction and molecular study, The mt-CO1 gene was amplified with a conventional polymerase chain reaction (PCR), the PCR product purified and DNA sequencing for reverse and forward strands was determined by a genetic analyzer, the obtained sequences aligned with the DNA sequences of T. hydatigena in Iran, Turkey and Palestine, which deposited in GenBank under the following accession number (JQ710588), (JN827307) and ( KM032284) respectively. The prevalence rate of C. tenuicollis was 2.63% in sheep and 2.58% in goats. This result shows no significant differences of C. tenuicollis between sheep and goats (p&gt;0.05). The nucleotide sequence alignment of cytochrome oxidase subunit 1 (CO 1) gene revealed that the amplified DNA fragment is belong to Taenia hydatigena and Echinococcus granulosus and the nucleotide sequences of T. hydatigena deposited in GenBank under accession number (MH638348). This finding concludes that the amplification of mt-CO1 gene cannot be depended on discriminate hydatid cyst and C. tenuicollis while the partial DNA sequences of mt-CO1 gene are significantly valuable to differentiate C. tenuicollis from hydatid cyst, which is completely different in the pathology and control.

Biochemical and Histopahthological Changes on Toxoplasma Infected Rats Treated with Lincocin and/ or Green Tea

Toxoplasma gondii is a blood parasite of felids with a wide range of intermediate hosts including humans. The present study was carried out to evaluate the efficacy of acute toxoplasmosis on liver, kidney functions and fertility hormones of infected rats, also the effect of Lincocin and green tea oil and their combination on improving the side effects of acute infection. A total number of 40 pathogen and Toxoplasma-free Sprague-Dawley rats were divided into four groups as follows: Group (1) non infectednon treated; Group (2) infected non treated, Group (3) infected and treated with Lincocin; Group (4) and infected and treated Lincocin and the addition of green tea. The recorded data revealed a significant elevation in levels of ALT, AST, T. Bilirubin, urea and creatinine and a significant decrease of the levels of albumin, progesterone, and testosterone in infected non- treated rats when compared with those of the non- infected group, while cortisol level was not affected. It could be concluded that T. gondii could affect liver and kidney functions and adversely affect major reproductive hormones. Therefore, it is recommended for the In Vitro Fertilization (IVF) and fertility centers to investigate T. gondii infection in the serum of infertile men as a routine test and treat the positive cases. Treatments with Lincocin plus green tea could be the drug of choice to avoid side effects of acute toxoplasmosis.

Calcium-dependent protein kinases are potential targets for Toxoplasma gondii vaccine.

Toxoplasma gondii belongs to the Apicomplexa phylum that caused a widespread zoonotic infection in wide range of intermediate hosts. Over one-third of the world's population are latently infected with T. gondii and carry it. The complex life cycle of T. gondii indicates the presence of a plurality of antigenic epitopes. During the recent years, continuous efforts of scientists have made precious advances to elucidate the different aspects of the cell and molecular biology of T. gondii. Despite of great progresses, the development of vaccine candidates for preventing of T. gondii infection in men and animals is still remains a challenge. The calcium-dependent protein kinases (CDPKs) belongs to the superfamily of kinases, which restricted to the apicomplexans, ciliates, and plants. It has been documented that they contribute several functions in the life cycle of T. gondii such as gliding motility, cell invasion, and egress as well as some other critical developmental processes. In current paper, we reviewed the recent progress concerning the development of CDPK-based vaccines against acute and chronic T. gondii.

A review of neosporosis and pathologic findings of Neospora caninum infection in wildlife.

Neospora caninum is an apicomplexan parasite that is the etiologic agent of neosporosis, a devastating infectious disease regarded as a major cause of reproductive loss in cattle and neuromuscular disease in dogs worldwide. This protozoan pathogen is maintained in the environment by a heteroxenous life cycle that involves a definitive canid host and a wide range of intermediate hosts. In recent years, a number of wildlife species have been investigated for their possible involvement in the N. caninum life cycle and many have been implicated as intermediate hosts. However, in many instances these studies have utilized serological and molecular techniques to detect infection in clinically normal animals, and investigation of possible associated morbidity, mortality, and pathology has been neglected. As such, the occurrence and importance of Neospora-associated disease in wildlife species are unknown. In order to improve our understanding of the significance of N. caninum infection in nondomestic species, the present review provides an up-to-date summary of clinical neosporosis and N. caninum-associated pathologic lesions in naturally and experimentally infected wildlife species. We provide a list of all free-ranging and captive wildlife species identified with N. caninum infection to date using currently available diagnostic tools. The advantages and disadvantages of diagnostic methods in wildlife are addressed in order to recommend optimal diagnosis of confirming N. caninum infection and neosporosis in nondomestic species. Although current data would suggest that N. caninum infection does not adversely impact wildlife populations, there is a need for greater international uniformity in the diagnosis of N. caninum infection and neosporosis in nondomestic species in order to assess the true consequences of parasite infection.

Systems-based analysis of the Sarcocystis neurona genome identifies pathways that contribute to a heteroxenous life cycle.

ABSTRACTSarcocystis neurona is a member of the coccidia, a clade of single-celled parasites of medical and veterinary importance including Eimeria, Sarcocystis, Neospora, and Toxoplasma. Unlike Eimeria, a single-host enteric pathogen, Sarcocystis, Neospora, and Toxoplasma are two-host parasites that infect and produce infectious tissue cysts in a wide range of intermediate hosts. As a genus, Sarcocystis is one of the most successful protozoan parasites; all vertebrates, including birds, reptiles, fish, and mammals are hosts to at least one Sarcocystis species. Here we sequenced Sarcocystis neurona, the causal agent of fatal equine protozoal myeloencephalitis. The S. neurona genome is 127 Mbp, more than twice the size of other sequenced coccidian genomes. Comparative analyses identified conservation of the invasion machinery among the coccidia. However, many dense-granule and rhoptry kinase genes, responsible for altering host effector pathways in Toxoplasma and Neospora, are absent from S. neurona. Further, S. neurona has a divergent repertoire of SRS proteins, previously implicated in tissue cyst formation in Toxoplasma. Systems-based analyses identified a series of metabolic innovations, including the ability to exploit alternative sources of energy. Finally, we present an S. neurona model detailing conserved molecular innovations that promote the transition from a purely enteric lifestyle (Eimeria) to a heteroxenous parasite capable of infecting a wide range of intermediate hosts.

A molecular survey on host specificity of feline and canine Hepatozoon in model site of northern Kenya

Species of the genus Hepatozoon are apicomplexan parasites transmitted by variety of hematophagous arthropods to a wide range of intermediate hosts. Hepatozoon infections are broadly distributed around the world and the presence of this parasite is confirmed both in cats and dogs. Until now, two species from canines (H. canis, H. americanum) and a single species from felines (H. felis) have been reported. While the canine Hepatozoon spp. are transmitted by ticks, the vector for H. felis remains unknown. The aim of presented study was to determine the prevalence and the diversity of Hepatozoon in population of domestic cats and dogs living in close contact in rural communities of Samburu pastoralists in northern Kenya and to evaluate the existence of possible cross-transmissions between both hosts. Between years 2007-2012 in total, 135 and 258 blood samples from cats and dogs from the area of Mt. Kulal (5 localities) was collected, respectively. The DNA from blood (preserved in ethanol) was extracted using phenol-chlorophorm method and followed by conventional PCR screening. First round of PCR was done by using Piroplasmid-F and Piroplasmid-R primers, amplifying 18S rRNA gene of Hepatozoon spp. (400 bp). A second PCR assay was performed in samples positive by Piroplasmid primers to amplify a larger fragment (1400 bp) of the 18S rRNA gene. All PCR amplicons comming from positive samples were sequenced and determined according to the BLAST match. In cats, this revealed 110 out of 135 (81.5%) positive samples, of which we obtained 104 sequences with an identity of 98% -100% to an existing GenBank accession. In total, 77 sequences were confirmed as Hepatozoon felis, 26 samples was proven to be Hepatozoon sp. and a single sample was determined as Hepatozoon canis with an identity of 96%. Regarding dogs, 121 out of 258 (47%) were positive and we gained 107 sequences of which 105 showed similarity to Hepatozoon canis and the remaining two proved to be Hepatozoon sp. Despite a close contact of hosts, obviously cats and dogs do not share the same parasite, which demonstrates a great majority of clearly identified Hepatozoon canis/Hepatozoon felis. Mentioned facts could be explained either by strict host specificity or by presence of different vector or by both statements.

A mathematical model for within-host &lt;em&gt;Toxoplasma gondii&lt;/em&gt; invasion dynamics

Toxoplasma gondii (T. gondii) is a protozoan parasite that infects a wide range of intermediate hosts, including all mammals and birds. Up to 20% of the human population in the US and 30% in the world are chronically infected. This paper presents a mathematical model to describe intra-host dynamics of T. gondii infection. The model considers the invasion process, egress kinetics, interconversion between fast-replicating tachyzoite stage and slowly replicating bradyzoite stage, as well as the host's immune response. Analytical and numerical studies of the model can help to understand the influences of various parameters to the transient and steady-state dynamics of the disease infection.

Protozoal Hepatitis Associated with Immunosuppressive Therapy in a Dog

Protozoal Hepatitis Associated with Immunosuppressive Therapy in a Dog

The pathogenic helminth parasites of eels

Although 63 and 55 species of helminths have been reported from each species of Atlantic eel and from 29 to 19 for each species of Pacific eel only the monogeneans Pseudodactylogyrus bini and P. anguillae and the nematode Anguillicola crassus, originally specific to species of Pacific eels, can be considered serious pathogens. None of the three are normally pathogenic to their preferred natural eel host species in the wild. Pseudodactylogyrus spp. only cause serious local gill damage when present on a host in large numbers under optimal conditions that facilitate transmission. This is the case in eel aquaculture, where infections can be controlled by drugs. Anguillicola crassus is only pathogenic to Anguilla anguilla and A. rostrata when Atlantic eels are introduced to the far east or when the parasites have been introduced to Europe. Here the parasite life cycle differs in that A. crassus can infect a wide range of intermediate hosts, employ paratenic hosts and survive as larvae for months in the swimbladder wall. This makes it an excellent colonizer. Its major pathogenic effects on eels result from haemorrhaging in, and thickening of, the swimbladder wall. It reduces the oxygen concentration in the swimbladder, reducing its ability to function as a hydrostatic organ, and increases the stress response of eels. In shallow lakes at warm temperatures this can result in mass mortalities. It is also feared that the parasite affects the ability of eels to migrate to the Sargasso Sea and so contributes to the decline in eel populations. Control by drug treatment is possible in culture, but not in the wild.