Magnetic resonance imaging of the brain and skull of sheep with cerebral coenurosis

Treatment and management of coenurosis by Taenia multiceps: field data from outbreaks in endemic regions and literature review

BACKGROUND

Taenia multiceps coenurosis is endemic in sheep from various regions worldwide. Dogs, the key hosts, shed T. multiceps eggs in their feces contaminating the pasture, and lambs are mostly infected during their first turnout into pastures. The disease is manifested in two forms: acute (due to the migrating oncospheres in the CNS) or chronic (due to the developing coenuri in the brain or spinal cord). Both forms are frequently accompanied by neurological symptoms.

METHODS

Field trials conducted in an endemic region (Sardinia, Italy) to treat replacement lambs in six sheep flocks infected with acute coenurosis are summarized in this article. The article also reviews earlier reports on various approaches developed to treat and immunize sheep against coenurosis.

RESULTS

Accurate detection of the time in which lambs become infected is crucial in deciding which treatment approach should be used. Acute disease can be successfully treated via chemotherapy. Results of field trials conducted in Sardinia revealed the efficacy of three (1-week apart) oxfendazole doses (14.15 mg/kg) in protecting apparently healthy lambs in the infected flocks from developing neurological symptoms. A single praziquantel dose (18.75 mg/kg) worked well for the same purpose and was also found significant in treating 5 of 16 clinically ill lambs in one flock. Earlier reports documented high rates of recovery (up to 100%) in clinically diseased lambs that received much higher doses (50-100 mg/kg) of praziquantel. However, chemotherapy is not preferred in chronic coenurosis since it can lead to rupture of the coenuri, giving rise to serious inflammation in the CNS. Surgical intervention is highly recommended in this case, and the pooled success rates for surgery in chronic-infected cases was estimated at 82.1% (95% CI 73.1-91.0%). However, various trials have been conducted to immunize sheep against T. multiceps coenurosis, and the 18k (Tm18) family of oncosphere antigens was found promising as a vaccine candidate.

CONCLUSIONS

In acute coenurosis, selection of the proper anthelmintic should be done after consulting the owner for several reasons: (1) costs of the used anthelmintic: treating a small flock of 100 sheep costs around 1170 and 660 € for praziquantel and oxfendazole, respectively; (2) withdrawal time of the used anthelmintic: No time is required before consuming meat and milk from praziquantel-treated sheep, whereas meat and milk from oxfendazole-treated sheep should not be consumed for 44 and 9 days, respectively, causing additional costs for the farmers. Since no commercial vaccines have yet been developed against T. multiceps coenurosis in sheep, preventive measures remain the cornerstone of controlling this serious disease.

Ultrasonography of Parasitic Diseases in Domestic Animals: A Systematic Review

Simple Summary

The aim of this literature review was to summarize the current knowledge on the application of ultrasonography in diagnosis, staging and monitoring of helminthic diseases in domestic animals. We selected and analyzed 122 papers about the application of ultrasonography in parasitic disease in ruminants, equids, swine, and companion animals. Helminths can be recognized in ultrasound images by their morphology, size, and location. In some cases, the parasites are not directly seen by ultrasound, but the lesions caused by them can be easily visualized. Ultrasound imaging is taking on an increasingly important role in veterinary parasitology.

Abstract

The aim of this review was to summarize the current knowledge on the application of ultrasonography in diagnosis, staging and monitoring of helminthic diseases in domestic animals. Only peer reviewed papers written in English language were included in this systematic review. All papers concerning unicellular parasites, wild animals, non-domestic experimental animals, or ex vivo or in vitro applications of ultrasonography were excluded from the review. A total of 122 papers met the inclusion criteria. Among them 47% concerned nematodes, 37% cestodes, and 16% trematodes with the genus Dirofilaria, Echinococcus, and Fasciola the most represented, respectively. Helminths can be recognized in ultrasound images by their morphology, size, and location. In some cases, the parasite stages are not directly seen by ultrasound, but the lesions caused by them can be easily visualized. Ultrasound imaging is taking on an increasingly important role in the diagnosis, staging, monitoring, and control of parasitic diseases in veterinary medicine. However, it cannot replace the clinical approach and the diagnostic tests commonly used in veterinary parasitology.

Taenia multiceps coenurosis: a review

Taenia multiceps is a taeniid cestode that inhabits the small intestines of both wild and domestic carnivores. The larval stage, Coenurus cerebralis, is typically found in the central nervous system (CNS) of a wide range of livestock and, to a lesser extent, in the extra-cerebral tissues of sheep and goats. This review covers all aspects of the life cycle of T. multiceps and its epidemiology, molecular characterization, pathogenesis, diagnosis, therapy, control and zoonotic potential. Coenurosis caused by the larval stage of T. multiceps has a worldwide distribution and is often fatal in intermediate hosts, which can result in substantial economic losses in livestock farming. Molecular characterization using the mitochondrial genes cytochrome c oxidase subunit 1 and nicotinamide adenine dinucleotide dehydrogenase subunit 1 of different T. multiceps populations has revealed significant genetic variation and the presence of three major haplotypes. The disease mostly affects young sheep and is referred to as either acute or chronic coenurosis. Acute coenurosis occurs as a result of oncospheres migrating through the CNS, while chronic coenurosis occurs as a consequence of the coenurus maturing, which causes displacement and pressure atrophy of brain tissue. Non-cerebral coenurosis has been most commonly reported in goats. The best diagnostic method for cerebral coenurosis involves the interpretation of clinical signs with accurate localization of the cyst using diagnostic imaging techniques. A vaccine based on recombinant oncosphere antigens has proved to be an effective tool against T. multiceps infection in sheep. Additionally, use of anthelmintics during the parasite's migration stages reduces the development of cysts in the sheep brain. Surgery is considered the most effective method for the treatment of cerebral coenurosis in small ruminants, but is often not carried out because of the limited finances of many sheep and goat breeders. However, coenurosis can also be controlled effectively through preventative measures, such as anthelmintic treatment of dogs and the proper disposal of intermediate host carcasses. The parasite is also zoonotic, and cases of coenurosis have been reported in humans with coenuri located in the brain, spinal cord and eyes.

First molecular confirmation of Coenurus cerebralis in sheep and goats with neurological behaviors in Iraq

Background and Aim:

Coenurus cerebralis is the intermediate stage of the canine cestode, which infect sheep and goats, resulting mainly in neurological signs and causing direct and indirect economic losses. This study aimed to demonstrate the existence of C. cerebralis and to elucidate the role of this parasite in inducing neurological behaviors in sheep and goats.

Materials and Methods:

On the basis of historical data on neurological signs, we subjected 76 animals (49 sheep and 27 goats) of different ages, sexes, and geographical areas for molecular examination of their blood samples using the polymerase chain reaction assay.

Results:

Of the 76 animals, 23.68% tested positive for C. cerebralis infection. We found significant increases in infection (p<0.05) in sheep (26.53%) more than in goats (18.52%). Circling movement was prevalent significantly among both C. cerebralis-positive sheep and goats. The Nineveh region had a significant (p<0.05) increase in positive sheep and goats, and the sheep of all study regions were infected significantly (p<0.05) more than were the goats. We found no significant (p>0.05) variation between sheep ages ≥1-3 years and ≥3 years; however, both groups had a significantly (p≤0.043) higher positivity rate than did sheep ages <1 year. The findings of sheep ages <1 year and ≥1-3 years were significantly higher than those of the goats, but not for goats ages ≥3 years. Female sheep and goats showed a significant increase in positivity versus that for the males.

Conclusion:

To the best of our knowledge, this study is the first report in Iraq targeting detection of C. cerebralis in sheep and goats with neurological behaviors; therefore, additional studies involving different animals in other regions using molecular techniques are needed.

Are current practices of yak herdsmen adequate to combat Coenurosis in Laya Bhutan?

Background

Coenurosis, known commonly as gid, is caused by a tapeworm Taenia multiceps. It is a disease of small ruminants globally but also occurs in large ruminants, especially in yak in the Himalaya. Gid is a pathological condition in young yaks, mostly below 3 years of age. The infected animal displays a circling movement with the head tilting towards the location of the cyst of a tapeworm on the cerebral surface of the brain.

Objective

We conducted a study with the primary aim to gain an insight into yak herdsmen's practices to manage Coenurosis in the Laya administrative block of Bhutan.

Methods

All seven villages of Laya were included for sampling. Seventy‐five out of 182 households owned yaks, and 54 yak‐owning households were selected randomly. The government livestock officials of nine yak‐rearing highland districts were also included in the study. A cross‐sectional study was conducted based on a questionnaire survey and focussed mainly on herdsmen's practices to manage gid. Two sets of questionnaires were used for yak herders and livestock officials. Each predesigned questionnaire was semi‐structured and consisted of both open– and closed‐ended questions.

Results

The study revealed gid as a major cause of yak mortality. Gid occurred more in winter during migration and most herders lost one to three yaks annually. Herdsmen kept an average of two watchdogs and dewormed them once annually. Similarly, calves were also dewormed once annually. The carcasses of dead yaks were fed to dogs. Livestock officials were optimistic about controlling the disease in the future, despite the yak areas being difficult to access. Most herders had not attended the gid awareness programme. The animal health worker visited herds once annually. In absence of animal health workers, most herdsmen resorted to different practices to treat affected yaks –the most common practice being surgery. Gid was mentioned to harm herdsmen's economy.

Conclusions

The study concluded that for effective management of gid in Laya, livestock agencies must create more awareness on gid, increase the frequency of visits by animal health workers to yak herds, and increase the frequency of deworming of watchdogs and calves.

GP50 as a promising early diagnostic antigen for Taenia multiceps infection in goats by indirect ELISA

Background

Coenurosis is caused by coenurus, the metacestode of Taenia multiceps, which mainly parasitizes the brain and spinal cord of cattle, sheep and goats. To date, no widely-approved methods are available to identify early coenurus infection.

Methods

In this study, we identified a full-length cDNA that encodes GP50 (TmGP50) from the transcriptome of T. multiceps, and then cloned and expressed in E. coli. The native proteins in adult stage and coenurus were located via immunofluorescence assays, while the potential of recombinant TmGP50 protein (rTmGP50) for indirect ELISA-based serodiagnostics was assessed using native goat sera. In addition, we orally infected 20 goats with mature T. multiceps eggs. Praziquantel (10%) was given to 10 of the goats 45 days post-infection (p.i.). Blood samples were collected for 17 weeks p.i. from the 20 goats and anti-rTmGP50 antibodies were evaluated using the indirect ELISA established here.

Results

The TmGP50 contains an 897 bp open reading frame, in which signal sequence resides in 1 ~ 48 sites and mature polypeptide consists of 282 amino acid residues. Immunofluorescence staining showed that native TmGP50 was localized to the microthrix and parenchymatous zone of the adult parasite and coenurus, and the coenurus cystic wall. The indirect ELISA based on rTmGP50 exhibited a sensitivity of 95.0% and a specificity of 92.6% when detecting GP50 antibodies in sera of naturally infected goats and sheep. In goats experimentally infected with T. multiceps, anti-TmGP50 antibody was detectable from 2 to 17 weeks p.i. in the control group, while the antibody fell below the cut-off value about 3 weeks after praziquantel treatment.

Conclusion

Our results indicate that recombinant TmGP50 is a suitable early diagnostic antigen for coenurus infection in goats.

Is the red fox (Vulpes vulpes) a competent definitive host for Taenia multiceps?

Background

Shepherd and stray dogs are thought to represent the primary definitive hosts of Coenurosis by Taenia multiceps, due to their feeding habits which translate into high chances of coming into contact with infected intermediate hosts. Nonetheless, little attention has been paid to the role of the red fox (Vulpes vulpes) in the epidemiology of coenurosis. In fact a knowledge gap exists on the role played by red foxes in the epidemiology of Taenia multiceps and the capability of this parasite to produce fertile and viable eggs in this wild canid, i.e. on the occurrence of a sylvatic cycle.

This study investigates the role of the red fox (Vulpes vulpes) in the epidemiology of T. multiceps and related metacestodoses.

Methods

The small intestine of 63 red foxes was macroscopically examined for the presence of cestodes. Adult parasites were identified morphologically as being T. multiceps. Tapeworm eggs were counted and stored at 4 °C in physiological saline solution prior to experimental infection of four sheep and one goat. Sheep were inoculated orally on Day 0 with 3000 (sheep 1), 5000 (sheep 2 and 3) or 7000 eggs (sheep 4), while the goat was infected with 5000 eggs of T. multiceps. The animals were followed-up regularly by MRI and underwent surgical treatment between days 180 to day 240 post infection. Collected coenuri were identified using morphological and molecular methods.

Results

A total of 6.3 % of red foxes were found infected with T. multiceps and the eggs obtained from the worms were determined to have a viability of 45.4 %. Two of the challenged sheep and the goat developed disease compatible with T. multiceps. Morphometrical features of the cysts were consistent with those of T. multiceps; nucleotide amplification and sequencing of mitochondrial genes (i.e., cox1 and Nd1) from the metacestode material confirmed the identification.

Conclusions

The present study is the first to provide evidence of the role of the red fox as a competent definitive host for T. multiceps, thus changing the epidemiological scenarios of infections by this cestode.

Molecular characterization of enolase gene from Taenia multiceps

Taenia multiceps is a cestode parasite with its larval stage, known as Coenurus cerebralis, mainly encysts in the central nervous system of sheep and other livestocks. Enolase is a key glycolytic enzyme and represents multifunction in most organisms. In the present study, a 1617bp full-length cDNA encoding enolase was cloned from T. multiceps and designated as TmENO. A putative encoded protein of 433 amino acid residues that exhibited high similarity to helminth parasites. The recombinant TmENO protein (rTmENO) showed the catalytic and plasminogen-binding characteristics after the TmENO was subcloned and expressed in the pET30a(+) vector. The TmENO gene was transcribed during the adult and larval stages and was also identified in both cyst fluid and as a component of the adult worms and the metacestode by western blot analysis. Taken together, our results will facilitate further structural characterization for TmENO and new potential control strategies for T. multiceps.

Application of polymerase chain reaction on cerebrospinal fluid for diagnosis of cerebral coenurosis in small ruminants

Sheep and goats serve as intermediate hosts for the canine tapeworm Taenia multiceps. The cysts produced by the intermediate stage of parasite are usually found in the cerebral hemispheres of small ruminants, and the resulting disease is commonly known as coenurosis. Coenurosis is clinically manifested in the form of various nervous symptoms, depending on the exact location of the cyst. The variety of neurological symptoms contributes to the complexity of clinical diagnosis and reinforces the need for a more specific and acceptable diagnostic approach. We demonstrated here, for the first time, that the T. multiceps DNA is present in the cerebrospinal fluid (CSF) of the infected sheep and goats. In addition, the molecular genetic marker of the mitochondrial DNA was applied phylogenetically to show that our isolates together with other T. multiceps strains comprised a monophyletic group that is a sister to Taenia krabbei. Pairwise comparison between the cox1 sequences of our study and other T. multiceps genotypes existing in the GenBank showed similarity ranging from 98 to 100%. Accordingly, the polymerase chain reaction (PCR) can be used for amplification of DNA of the parasite originated from the CSF and provides a valuable method for accurate identification of coenurosis cases.

Monitoring of parasitic cysts in the brains of a flock of sheep in Egypt

Cerebral parasitic cysts constitute a major problem for livestock. Among these, coenurosis and toxoplasmosis are predominant. Here, a total number of 60 sheep obtained from a private farm in Suez province, Egypt, were examined postmortem to detect visible parasitic cysts, and microscopically to detect small-sized entities. Necropsy revealed bladder-like cysts measuring 0.5-6.5 cm in diameter that were filled with a translucent fluid containing a large number of protoscolices. Accordingly, the cysts were identified as the metacestodeCoenurus cerebralis. Among the sheep examined, 11 animals (7 males and 4 females) (18.3%) were infected. Most of the cysts were located in the cerebral hemispheres, with numbers ranging from one to three per infected animal. The effect of the presence of cysts in the brain tissue was evaluated. Histopathologically, pseudocysts of the apicomplexan Toxoplasma gondii were found in two animals with no detectable inflammatory cell reactions. In conclusion, coenurosis and toxoplasmosis are serious parasitic problems that play a significant role in sheep management in Egypt, as a result of close contact between livestock and dogs and cats, which play a critical role in the life cycle of these parasites.