Pulmonary cystic echinococcosis

PURPOSE OF REVIEW

Pulmonary cystic echinococcosis, a zoonosis caused by the larvae of the dog tapeworm Echinococcus granulosus, is considered as a major public health problem in countries where dogs are used to care for large herds. Despite its frequency and widespread endemicity, the literature on pulmonary cystic echinococcosis is scarce and not systematic. We aimed to summarize currently available information to provide a comprehensive overview for clinicians facing cases of pulmonary cystic echinococcosis.

RECENT FINDINGS

Despite discrepancies in the literature, some patterns can be discerned. The ratio of lung:liver involvement is higher in children than in adults. Most pulmonary cases are discovered incidentally on routine radiograph evaluation; also most infected individuals remain asymptomatic until the cyst enlarges sufficiently to cause symptoms. Symptoms are usually caused by mass effect from the cyst. Complications (cyst rupture, aggregated infection) change the clinical presentation, producing cough, chest pain, hemoptysis, or vomica. Diagnosis is obtained by chest radiographs or computed tomography, and supported by serology. Presurgical chemotherapy reduces the chances of seeding and recurrence. Treatment with benzimidazoles is an option when surgery is unavailable or complete removal is unfeasible.

SUMMARY

Diagnosis of pulmonary cystic echinococcosis is primarily made by imaging, and surgery remains the main therapeutic approach.

Grass height and transmission ecology of Echinococcus multilocularis in Tibetan communities, China

BACKGROUND

Alveolar echinococcosis is a major zoonosis of public health significance in western China. Overgrazing was recently assumed as a potential risk factor for transmission of alveolar echinococcosis. The research was designed to further test the overgrazing hypothesis by investigating how overgrazing influenced the burrow density of intermediate host small mammals and how the burrow density of small mammals was associated with dog Echinococcus multilocularis infection.

METHODS

The study sites were chosen by previous studies which found areas where the alveolar echinococcosis was prevalent. The data, including grass height, burrow density of intermediate host small mammals, dog and fox fecal samples as well as Global Positioning System (GPS) position, were collected from field investigations in Shiqu County, Sichuan Province, China. The fecal samples were analyzed using copro-PCR. The worms, teeth, bones and hairs in the fecal samples were visually examined. Single factor and multifactor analyses tools including chi square and generalized linear models were applied to these data.

RESULTS

By using grass height as a proxy of grazing pressure in the homogenous pasture, this study found that taller grass in the pasture led to lower small mammals' burrow density (chi(2) = 4.670, P = 0.031, coefficient = -1.570). The Echinococcus multilocularis worm burden in dogs was statistically significantly related to the maximum density of the intermediate host Ochotona spp. (chi(2) = 5.250, P = 0.022, coefficient = 0.028). The prevalence in owned dogs was positively correlated to the number of stray dogs seen within a 200 meter radius (Wald chi(2) = 8.375, P = 0.004, odds ratio = 1.198).

CONCLUSIONS

Our findings support the hypothesis that overgrazing promotes transmission of alveolar echinococcosis and confirm the role of stray dogs in the transmission of alveolar echinococcosis.

Production of experimental hydatid cyst in the eye, peritoneum and liver of BALB/c mice

As the main treatment for this infection is surgery, the surgery team personnel are at the risk of the protoscoleces released from the hydatid cysts (HC) of patients. The first goal of this study was to determine the probability of the production of ocular HC in mice due to the fluid of the aspirated protoscoleces from the sheep liver with HC. The second goal of this study was to produce HC in the peritoneum and liver, in order to gather more information for future studies on hepatic and peritoneal HC treatment procedures. For the first goal of this study, different concentrations of protoscoleces were prepared and injected into the eyes of 60 mice. After 20 weeks, 10 of the 60 mice of this group died. The remaining 50 mice were examined by a surgeon under the anesthesia. There weren't any symptoms of HC in the eyes and around it. For the second goal, 39 new mice were separated into three sub groups and 0.5 ml of protoscolex solution was injected intraperitoneally. After 20 weeks, they were anesthetized and their peritoneum, intestines and liver were examined. HC was seen in the peritoneum and liver of 6 mice.

Problematic parasite to pet and owner

No visitor arriving at a UK air or seaport is left in any doubt about the British Government's wish to keep these islands free of rabies. But far less publicity is given to warnings about the threat posed to human health by another disease which may be carried by companion animals. John Bonner reports on the campaign to stop the fox tapeworm Echinococcus multilocularis from reaching these shores.

[The current risk factors for hydatidosis in Tunisia]

Hydatidosis is a major public health problem in Tunisia. The presence of numerous stray dogs, widespread practice of sheep rearing and frequent slaughter of animals outside slaughterhouses are the main risk factors for spread of this zoonotic disease. Human behaviour associated with poor understanding of the parasite life cycle also has a negative impact. Health education is crucial for effective control. It should emphasize the damaging effects of uncontrolled slaughter, the exact role of dogs in parasite transmission and above all the need for adequate measures to sterilize infested viscera.

[Transmission dynamic model for echinococcosis granulosus: establishment and application]

A dynamic model of disease can be used to quantitatively describe the pattern and characteristics of disease transmission, predict the disease status and evaluate the efficacy of control strategy. This review summarizes the basic transmission dynamic models of echinococcosis granulosus and their application.

[Risk of Echinococcus granulosus becoming endemic in Dutch cattle]

Echinococcus granulosus is rare in The Netherlands and most human patients originate from southern Europe and Africa, where E. granulosus is still endemic in sheep, cattle, and pigs. Since the accession of some south-eastern European countries to the European Union, a large number of cattle have been imported from this area, according to national import data. The objective of this study was to determine the risk of re-introduction of E. granulosus in The Netherlands via the import of cattle from these endemic areas. The number of infected imported cattle was determined by correcting the number of imported cattle with the national animal prevalence of E. granulosus in the country of origin. In 2007, the number of imported E. granulosus-infected cattle varied from 0 (Cyprus) to 4,934 (Romania, accounting for 90% of all positive cattle). The likelihood of detecting E. granulosus at slaughter is low--we assumed, based on confirmed cases, that only 10% of infected cattle will be detected during visual inspection at slaughter. In 2007, 542 infected cattle were probably culled in The Netherlands (assuming that cattle younger than 3 months were not infected). Since the lungs and livers of cattle approved for human consumption may be processed into dog food, there is a risk that dogs that eat E. granulosus-containing dog food may become infected and in turn infect humans. On the basis of a model that assumed that only cattle older than 3 months at the moment of importation were a risk, 23 dogs may have been exposed to E. granulosus in 2007. To reduce the risk of importing E. granulosus, measures should be taken, such as declaring the lungs and livers of Romanian cattle unfit for human consumption and banning the use of infected raw lung and liver in dog food.

[Reintroduction of E. granulosus by import of cows in the Netherlands]

Since East European countries joined the EU, the import of both dairy and beef cows from these countries increased considerably. Based on the identification and registration system it turned out that in the period from May until December 2007 about 200 cows per month were imported from Romania. These animals were either slaughtered immediately or in autumn. In autumn, cysts were noticed both in slaughtered cows during meat inspection and in deceased animals (originated from Romania) during postmortem investigation performed by the Animal Health Service. Because cysts were strongly reminiscent of Echinococcus granulosus hydatid cysts, samples were sent to the authorized laboratory (National Reference Laboratory of Parasitology), where the reintroduction of this potentially zoonotic parasitic infection has been confirmed. The risks of reintroduction of E. granulosus in the Netherlands are described.

Cystic hydatidosis: a zoonotic silent health problem

Examination of five hundred pet dogs revealed Echinococcus granulosus in nine dogs, Dipylidium caninum in twenty dogs, and Toxocara canis in thirty dogs. The risky role played by pet dogs in the transmission and spreading of zoonotic cystic hydatidosis was discussed.

Canine echinococcosis in Kyrgyzstan: using prevalence data adjusted for measurement error to develop transmission dynamics models

Echinococcosis is a major emerging zoonosis in central Asia. A cross-sectional study of dogs in four villages in rural Kyrgyzstan was undertaken to investigate the epidemiology and transmission of Echinococcus spp. A total of 466 dogs were examined by arecoline purgation for the presence of Echinococcus granulosus and E. multilocularis. In addition, a faecal sample from each dog was examined for taeniid eggs. Any taeniid eggs found were investigated using PCR techniques (multiplex and single target PCR) to improve the diagnostic sensitivity by confirming the presence of Echinococcus spp. and to identify E. granulosus strains. A total of 83 (18%) dogs had either E. granulosus adults in purge material and/or E. granulosus eggs in their faeces as confirmed by PCR. Three genotypes of E. granulosus: G1, G4 and the G6/7 complex were shown to be present in these dogs through subsequent sequence analysis. Purge analysis combined with PCR identified 50 dogs that were infected with adult E. multilocularis and/or had E. multilocularis eggs in their faeces (11%). Bayesian techniques were employed to estimate the true prevalence, the diagnostic sensitivity and specificity of the procedures used and the transmission parameters. The sensitivity of arecoline purgation for the detection of echinococcosis in dogs was rather low, with a value of 38% (credible intervals (CIs) 27-50%) for E. granulosus and 21% (CIs 11-34%) for E. multilocularis. The specificity of arecoline purgation was assumed to be 100%. The sensitivity of coproscopy followed by PCR of the isolated eggs was calculated as 78% (CIs 57-87%) for E. granulosus and 50% (CIs 29-72%) for E. multilocularis with specificity of 93% (CIs 88-96%) and 100% (CIs 97-100%), respectively. The 93% specificity of the coprological-PCR for E. granulosus could suggest coprophagia rather than true infections. After adjusting for the sensitivity of the diagnostic procedures, the estimated true prevalence of infection of E. granulosus was 19% (CIs 15-25%) and the infection pressure in the dog population was estimated to be 0.29 infections per year (CIs 0.014-0.75). Logistic regression analysis failed to identify any significant risk factors for infections for E. granulosus. After adjusting for the sensitivity of the test procedures, the estimated true prevalence for E. multilocularis was 18% (CIs 12-30%). Dogs that were restrained had a significantly lower prevalence of E. multilocularis of 11% (CIs 6-29%) compared with 26% in free-roaming dogs (CIs 17-44%) and independently within these groups hunting dogs were more likely to be infected than non-hunting dogs.

Prevalence of echinococcosis in street dogs in Tripole District, Libya

Cystic echinococcosis due to E. granulosus is a serious public health and livestock economy problem in Libya. Kato thick smear examination of 50 street dogs stools showed that they had Echinococcus granulosus (58%), Taenia spp. (14%), Diplydium caninum (16%), Toxocara canis (121%) and 20% were parasite-free. The stool examination using Kato thick smear was more sensitive and more specific that the indirect haemaggutination test. The results were discussed with general review of the disease in Libya.

The prevalence, organ distribution and fertility of cystic echinoccosis in feral pigs in tropical North Queensland, Australia

An investigation was carried out to study the prevalence of Echinococcus granulosus hydatidosis in feral pigs (Sus domesticus) in the Charters Towers region of tropical North Queensland. Data were collected from a total of 238 carcasses, which were hunted and shot in the Burdekin River catchment area. Organs of the abdominal, thoracic, and pelvic cavities were examined for the presence of hydatid cysts. In the laboratory, cysts and hydatid cyst fluids were examined under a stereoscopic binocular microscope and a compound microscope. An overall prevalence of E. granulosus hydatid cysts in feral pigs was found to be 31.1%. There was no significant difference in either sex or age between infected and non-infected feral pigs. The predilection sites of cysts were livers (23%) and lungs (62%), with more cysts in lungs (252) than livers (48). The ratio of livers to lungs infected with fertile cysts was 1:4 compared to 1:8 sterile cysts. The overall fertility of cysts was 70.1%. The percentage of fertile cysts in liver and lung was 79.2% and 68.7%, respectively. The diameter of fertile cysts ranged from 15 to over 60 mm. There was no significant difference in size between fertile and non-fertile cysts in lungs. The high prevalence rate and fertility of cysts in feral pigs confirm that feral pigs can take part in the sylvatic cycle of the parasite in the region. The public health significance of this observation is potentially very important.

Echinococcosis granulosus/hydatidosis an endemic zoonotic disease in Egypt

The hydatidosis patients were collected from Mansoura University's Hospitals and Dakahlia Public Health Hospitals. The patients were divided into three groups: GI: 74 patients with surgically confirmed cystic echinococcosis (CE), GII: 45 patients with other parasitic infections, GIII: 30 healthy parasite-free individuals. All were subjected to questionnaire and full clinical examination, imaging investigation, routine laboratory examination, and serum samples for antibody against CE by the specific ELISA. The hydatidosis was higher in females but without statistically significant difference (p = 0.309). There was no age predilection difference regarding hydatidosis infection. However, the hydatidosis granulosus was significantly higher in the shepherd followed by the farmers. All the questionnaires were positively correlated to hydatidosis infection except the availability of clean domestic water and personal knowledge about hydatidosis gave negative correlations. The ELISA-OD correlated positively with the imaging investigation (mainly U S stage). The sensitivity of ELISA was 86.7% and specificity was 81.4%. The results were evaluated regarding the local and regional data on echinococcosis/hydatidosis.

Echinococcosis granulosus in stray dogs and Echino-IHAT in the hunters in Cairo, Egypt

A total of fifty stray dogs of both sex and of different ages were examined for natural infection with Echinococcus granulosus after post-mortem. Three main intestinal helminthes were recovered. These were in descending order of abundance Dipylidium caninum, Toxocara canis and E. granulosus. The latter worm was demonstrated in eight of them (16%). The sera of three out of 21 dog-hunters (14.3%) showed positive Echino-IHAT. Two of the hunters suffered Enterobius vermicularis and one of them had Taenia saginata as well. But, the abdominal X-ray of the two hunters was more or less normal and did not show any hydatid cyst.

Modelling the transmission of Echinococcus granulosus in dogs in the northwest and in the southwest of Morocco

Echinococcus granulosus (E. granulosus) infection was studied in 151 dogs in two regions of Morocco: 68 dogs in the northwest (Loukkos) and 83 dogs in the southwest (Tiznit). The mean prevalence rates of echinococcosis in dogs were 58.82% (46.23-70.63%) in Loukkos and 55.42% (44.10-66.34%) in Tiznit and the mean abundances of E. granulosus per dog were 75 (59-93) and 547 (504-595), respectively. The mean abundance of E. granulosus in dogs was fitted to a negative binomial distribution by the maximum likelihood techniques to define parameters. E. granulosus was aggregated in dogs in the two regions. The prevalence of infection and the abundance of E. granulosus in dogs were fitted to mathematical models in order to determine if the parasite population is partly regulated by definitive host immunity. The best fit was obtained with the models assuming the presence of immunity. The mean time of exposure to infection was similar in the two regions and ranged from 8 months to about 2 years. The infection pressures (number of E. granulosus) obtained per dog each year were 65 (8-294) in Loukkos and 476 (316-886) in Tiznit. The proportion of dogs susceptible to infection was still high along the life of the dogs in Loukkos, while it was not different from zero in old dogs of Tiznit.

Hydatidosis in camels (Camelus dromedarius) and their potential role in the epidemiology of Echinococcus granulosus in Iran

Hydatid cysts were recovered from 35.2% (233/661) of camels (Camelus dromedarius) slaughtered in five different regions of Iran. The degree of prevalence between males (34.4%) and females (36.6%) was not statistically significant. The highest rate of infection (59.3%) was found in the Isfahan region (in the central part of Iran) while the lowest (25.7%) was found in Kerman province. The organ distribution of cysts was 49.4% in lungs alone, 30.0% in both liver and lungs, 14.6% in liver only and 6.0% in other organs. Therefore, the lungs were the predominant sites of the hydatid cyst. The range in the number of cysts was 1–48 in infected animals. The majority of the camels had 1–5 cysts, with 21.9%, 11.6% and 5.6% of infected camels having 6–10, 11–20 and 21 or more cysts respectively. There was a direct relationship between the rate and intensity of infection and host age. The fertility rate of lung cysts (69.7%) was higher than that of liver cysts (58.7%) and other organs (50.0%) whilst the viability rate of protoscoleces of liver fertile cysts (80.3%) was significantly higher than that of lung cysts (55.8%) and other organs (57.1%). The role of camels in the epidemiology of Echinococcus granulosus in Iran is discussed.

Impact of overgrazing on the transmission of Echinococcus multilocularis in Tibetan pastoral communities of Sichuan Province, China

BACKGROUND

Overgrazing was assumed to increase the population density of small mammals that are the intermediate hosts of Echinococcus multilocularis, the pathogen of alveolar echinococcosis in the Qinghai Tibet Plateau. This research tested the hypothesis that overgrazing might promote Echinococcus multilocularis transmission through increasing populations of small mammal, intermediate hosts in Tibetan pastoral communities.

METHODS

Grazing practices, small mammal indices and dog Echinococcus multilocularis infection data were collected to analyze the relation between overgrazing and Echinococcus multilocularis transmission using nonparametric tests and multiple stepwise logistic regression.

RESULTS

In the investigated area, raising livestock was a key industry. The communal pastures existed and the available forage was deficient for grazing. Open (common) pastures were overgrazed and had higher burrow density of small mammals compared with neighboring fenced (private) pastures; this high overgrazing pressure on the open pastures measured by neighboring fenced area led to higher burrow density of small mammals in open pastures. The median burrow density of small mammals in open pastures was independently associated with nearby canine Echinococcus multilocularis infection (P = 0.003, OR = 1.048).

CONCLUSION

Overgrazing may promote the transmission of Echinococcus multilocularis through increasing the population density of small mammals.

Hydatid disease of the spleen (report of 2 cases)

Hydatid disease is endemic in Middle East as well as other parts of the world including New Zealand and Australia [Altinors N, Senveli E, Donmez T, Bavbek M, Kars Z, Sanli M. Management of problematic intracranial hydatid cyst. Infection 1995;23:283-7]. Passing eggs from definite hosts--dogs and some wild carnivores--are ingested by intermediate hosts--humans and herbivores [Begg I, The radiology of hydatid disease. Am J Roentgenol 1985;145;639-48]. Larva penetrate the intestinal mucosa and reach the circulation, lodging and encysting in the body organs [Vahedian-Ardakani J. Hydatid cyst of the liver presenting as cutaneous abscesses. Ann Saudi Med 1997;17(2);235-7]. Liver and lungs account for more than 90% of organ involvements. Splenic involvement is rare occurrence of about 2.5%. [Franquet T, Montes M, Lecumberri FJ, Esparza J, Bescos JM. Hydatid disease of the spleen: imaging findings in nine patients. Am J Roentgenol 1990;154:525-8]. Here we report two cases of hydatid disease of the spleen in Izeh, a city in Khuzestan Province of Iran.

Current control strategies targeting sources of echinococcosis in Japan

The authors describe the current control strategies targeting definitive hosts of the most important zoonotic parasite in Japan, Echinococcus multilocularis. A dramatic increase in the prevalence of echinococcosis in foxes in Hokkaido (the second largest of Japan's islands), the invasion of wild foxes into urban areas, infection among pet and stray dogs, and the possibility of spreading the disease to the main island of Japan (Honshu)--all these pose significant threats to public health. Previous research findings and current strategies such as control measures against infections in wild foxes, suggest that it will be possible to eliminate echinococcosis in the future. The enforcement of a national reporting system for veterinarians, international collaboration, and the establishment of a Forum on Environment and Animals (FEA) give further reason to believe that success is possible. This is the first report of a multifaceted control strategy against echinococcosis in definitive hosts that includes collaborative efforts with local residents. This model might provide new ideas for Veterinary Services worldwide in their efforts to control other related zoonotic diseases.

Expression and diversity of Echinococcus multilocularis AgB genes in secondarily infected mice: evaluating the influence of T-cell immune selection on antigenic variation

The T-cell-mediated immune response exhibits a crucial function in the control of the intrahepatic proliferation of Echinococcus multilocularis larvae in mice and humans, both being natural intermediate hosts of the parasite. Antigen B (AgB), a metabolized Echinococcus spp. lipoprotein, contributes to the modulation of the T-cell immune response, and distinct sites of the corresponding AgB1, AgB3 and AgB4 genes were shown to be under positive selection pressure. Since several AgB gene variants are present in a single Echinococcus metacestode, we used secondary E. multilocularis infections in BALB/c and in athymic nude mice (devoid of T-cell responses) to analyze the effect of the cellular immune response on the expression and diversity of EmAgB1-EmAgB4 genes. We demonstrated hereby that EmAgB transcripts were less abundant in nude mice during the early phase of infection (at one month post-infection), and that EmAgB2 is simultaneously down-regulated when compared to the other three genes. A negative relationship exists between the level of transcription and diversity of EmAgB genes. Moreover, no excess of non-synonymous substitutions was found among the distinct EmAgB alleles from a single host. Together, these results pointed to the effect of purifying selection, which seemed to eliminate the detrimental AgB variants generated during the development of the metacestode within the peritoneal cavity of its intermediate host.