Cystic echinococcosis in the sheep: causes of its persistence in Sardinia

The authors analyse the current epidemiological situation of sheep Cystic Echinococcosis (CE) in Sardinia, where the prevalence of ovine CE is still very high (70%) and this parassitosis is also frequently found in the human population. For this reason Sardinia represents a peculiar model for CE study, because there are particular conditions that allow Echinococcus granulosus to complete its life cycle. Some social and economical factors support the persistence of sheep CE: over 3 million Sarda breed heads are extensively bred; the presence, at farm level, of a strong relationship between dog, sheep and human; the low commercial value of meat coming from adult sheep, whinch results in a large number of sheep being slaughtered at home or on the farm rather than in authorized slaughterhouses. Moreover Sardinia is the only Italian region where partially successful echinococcosis control plans have been applied. The authors suggest some indirect and direct initiatives, including the use of a new vaccine against the development of this metacestode in sheep, to reduce the prevalence of CE.     

Cystic echinococcosis in Sardinia: farmers' knowledge and dog infection in sheep farms

Cystic Echinococcosis (CE) is one of the most widespread parasitic diseases in Sardinia, the second largest Mediterranean island where almost 3,558,000 milk sheep were raised extensively. The aim of this survey was to evaluate the level of farmers' knowledge on CE transmission, focusing on the role of human to facilitate the persistence of this zoonosis in Sardinia after 14 years after the last campaign against CE. The other goal of the survey is to update on presence of Echinococcus granulosus in its definitive hosts through three ELISA coproantigen tests. An interview was carried out with 172 farmers. The questionnaire was designed to include possible factors associated with the transmission of Echinococcosis: ownership and number of dogs, the use of anthelmintic drugs against dog cestode, frequency of anthelmintic treatment in dogs, home slaughtering and offal disposal. Individual faecal samples were retrieved from 300 dogs, and after a preliminary macroscopic examination to discover adult worms and/or proglottids, was submitted to copromicroscopic examination. Coproantigens were then extracted according to the protocol described by Allan et al. (1992), and subsequently stored at -20°C until use. Faecal soluble antigens from E. granulosus were detected using three different ELISA coproantigen assays: (a) the commercially produced Chekit Echinotest (Bommeli, Bern, CH) based on polyclonal antibodies against adult excretory/secretory (E/S) antigens; (b) a sandwich ELISA that uses rabbit polyclonal antibodies against adult E/S antigens and biotinylated monoclonal antibody EmA9 produced against adult Echinococcus multilocularis somatic extract (Malgor et al., 1997); and (c) a sandwich assay that uses monoclonal antibody EgC3 produced by immunization with adult E. granulosus E/S products (Casaravilla et al., 2005). Questionnaire results reveal that on all farms home-slaughtering was done, and offal was used as dog meal raw (17%) or after boiling (37%), discarded in the trash (23%), or buried superficially (15%). Most farmers (69%) declared to deworm their dogs, but only 10% used cestodicidal drugs. The coprological survey of 300 farm dogs using sedimentation, flotation and three different coproantigen (CA) ELISAs resulted in a faecal prevalence of 8.3% for taeniid eggs, while the CA tests gave prevalences of 3% (Chekit Echinotest, Bommeli), 6% (EmA9 sandwich ELISA) and 10% (EgC3 sandwich ELISA). Our results show that this is not only an educational problem, but also an economic one, stressing the need that future control plans should follow an integrative approach including veterinary and medical services, farmers, breeders' associations and the Government.     

Cystic echinococcosis in the Falkland Islands

From 1991 to 1993, an investigation into the epidemiology of cystic echinococcosis (CE) was carried out in the Falkland Islands to evaluate the progress of the hydatid eradication campaign. The prevalence of CE in sheep was assessed using abattoir and farm slaughter data, and the exposure of dogs to the parasite was estimated using immunological techniques. A total of 59 466 sheep was examined at slaughter for E. granulosus and T. hydatigena cysts and the entire dog population of the Falkland Islands (n = 908) was examined by ELISA for the presence of specific serum antibodies to E. granulosus (IgG, IgA and IgE). In addition, a subsample of dogs (n = 464) was tested for the presence of E. granulosus antigens in faeces (copro-antigens). The prevalence of CE in sheep increased significantly during the period of the study from 0.11% in 1991 to 0.47% in 1993. Nineteen (2.1%) of 908 dog sera tested were seropositive, and eight dogs (1.7%) of 464 tested were positive in the copro-antigen assay. The combined use of abattoir surveillance, specific antibody and copro-antigen assay suggested that there were several locations in the Falkland Islands where the life cycle of E. granulosus may still perpetuate. Specific deficiencies in the eradication effort in those locations could be identified through follow-up questionnaires.     

Echinococcus granulosus infection in Spain

Cystic echinococcosis (CE) caused by the cestode Echinococcus granulosus is an endemic disease in Spain. Although specific control programmes initiated in the 1980s have led to marked reductions in CE infection rates in Spain, the disease still remains an important human and animal health problem in many regions of the country. Human incidence and livestock (including sheep, cattle, pigs and horses) prevalence data were gathered from national epidemiological surveillance information systems and regional institutions for the period 2000-2005. Additionally, data on the prevalence of E. granulosus infection in dogs were obtained from published literature. The most affected regions were those of the North Eastern, Central and Western parts of the country, (Autonomous Regions of Aragon, Castile-La Mancha, Castile-Leon, Extremadura, Navarre and La Rioja), where human CE incidence rates in the range of 1.1-3.4 cases per 10(5) inhabitants coexist with ovine/bovine CE prevalence rates up to 23%. Control programmes of hydatidosis/echinococcosis should be reinforced in these regions to reduce the prevalence of the disease.     

Prevalence and economic importance of cystic echinococcosis in slaughtered ruminants in Burdur,Turkey

This study was conducted between April 2000 and March 2001, in 12-month period. During the study, local slaughterhouses were visited periodically for 1 year to examine the internal organs (livers, lungs, spleens and hearts) for the presence of cysts and total 1355 cattle, 218 sheep and 104 goats were examined for the cystic echinococcosis (CE). It was found that 13.5% of cattle, 26.6% of sheep and 22.1% of goats were infected with this disease. While cysts in cattle (P < 0.001) and goats (P > 0.05) were found mostly in lungs (88.5 and 82.6%, respectively), but they were mostly found in livers (P > 0.05) in sheep. In addition to this, three spleens and one heart in cattle were infected with CE. In this study, the prevalence of CE and the number of cysts in ruminants were found different when the cattle, sheep and goats examined were stratified based on age. The prevalence and the number of cysts increased with age approaching an asymptotic prevalence of one in the oldest animals (P < 0.05). The number of cysts in cattle, sheep and goats were increasing at a rate of 0.31, 0.63 and 0.42/year, respectively. The economic decrease in the value of the carcasses because of the discarded liver and lung as a result of CE was estimated as 1.1% (7.5 US dollars per cattle) for cattle, 4.37% (3.2 US dollars per sheep) for sheep and 4.26% (2.9 US dollars per goat) for goats. The minimum total loss for all infected animals was determined to be 583 US dollars in infected animals, based on the market prices in the year 2002.     

The seroprevalence of Toxoplasma gondii in Ontario sheep flocks

In a random sample of 103 sheep farms in Ontario, 99% of the farms had some sheep serologically positive for Toxoplasma gondii, based on an enzymelinked immunosorbent assay (ELISA). The percent of sheep affected within farms ranged from 3.8% to 97.8%, with an average flock prevalence of 57.6%. When farm management variables were considered in a multivariate analysis, significantly lower rates of serologically positive sheep were associated with neutering of female cats and clipping of ewes' perineums before lambing; significantly higher prevalence rates were found on farms where sheep were purchased from other flocks, pigs were raised on the same farm, sheep shared pasture with other animals, flowing water was available at pasture, and pastured replacements had access to housing. As well, in univariate analyses, higher prevalence was positively associated with an increasing number of cat litters born over the previous two years and offering creep feed or forage to lambs, and inversely with the amount of labor expended on sheep rearing.     

Prevalence and Economic Importance of Cystic Echinococcosis in Slaughtered Ruminants in Burdur,Turkey1

This study was conducted between April 2000 and March 2001, in 12‐month period. During the study, local slaughterhouses were visited periodically for 1 year to examine the internal organs (livers, lungs, spleens and hearts) for the presence of cysts and total 1355 cattle, 218 sheep and 104 goats were examined for the cystic echinococcosis (CE). It was found that 13.5% of cattle, 26.6% of sheep and 22.1% of goats were infected with this disease. While cysts in cattle (P < 0.001) and goats (P > 0.05) were found mostly in lungs (88.5 and 82.6%, respectively), but they were mostly found in livers (P > 0.05) in sheep. In addition to this, three spleens and one heart in cattle were infected with CE. In this study, the prevalence of CE and the number of cysts in ruminants were found different when the cattle, sheep and goats examined were stratified based on age. The prevalence and the number of cysts increased with age approaching an asymptotic prevalence of one in the oldest animals (P < 0.05). The number of cysts in cattle, sheep and goats were increasing at a rate of 0.31, 0.63 and 0.42/year, respectively. The economic decrease in the value of the carcasses because of the discarded liver and lung as a result of CE was estimated as 1.1% ($7.5 per cattle) for cattle, 4.37% ($3.2 per sheep) for sheep and 4.26% ($2.9 per goat) for goats. The minimum total loss for all infected animals was determined to be $583 in infected animals, based on the market prices in the year 2002.     

Prevalence and risk factors for Maedi-Visna in sheep farms in Mecklenburg-Western-Pomerania

Despite indications of a considerable spread of Maedi-Visna among sheep flocks in Germany, prevalence studies of this important infection are hardly available. Prior to any health schemes and guidelines, knowledge about regional disease distribution is essential. Depending upon herd size, 70 farms were randomly selected, of which 41 cooperated. A total of 2229 blood samples were taken at random and serologically examined. For assessment of selected farm characteristics a questionnaire exercise was conducted at all farms involved. The average herd prevalence is 51.2%, the within-herd prevalence is 28,8%. In the unvariate analysis of risk factors, small (10-100 sheep) and large (> 250 sheep) farms are more MVV-affected than medium sized farms. The average stable and pasture space per sheep is larger at non-infected- compared to infected farms. Owners judgement on general herd health turns out to be better at non-infected compared to infected farms. Taking infected farms only, the risk of within-herd prevalence above 20% is significant higher in crossbred than in purebred flocks.     

Contagious ecthyma in the live sheep export industry

Objective: To investigate control options for contagious ecthyma (scabby mouth) in Australian sheep exported live to the Middle East.
Design: Prevalence, vaccination and modelling studies.
Procedure: One hundred and forty weaner sheep (less than 1 year old) on each of 106 farms in Western Australia (WA) and 18 farm groups of adult wethers received at a WA commercial feedlot were examined for lesions of scabby mouth. Sheep on a total of 26 farms in 3 States were divided into treatment and control groups for the vaccination study. A simple deterministic compartmental model was developed to establish which parameters had the greater effect on disease prevalence.
Results: The proportion of farms with evidence of scabby mouth in weaner sheep was 23.6% and, on those farms with the disease, the overall prevalence was 6.1%. At the feedlot, 4 out of 18 farm groups had 5 or more sheep with lesions on arrival. The overall prevalence in the 4 diseased groups was 5.2%. Sheep vaccinated on farm before trucking to the feed-lot had a lower prevalence of scabby mouth at the end of simulated shipping than controls. The main determinant of scabby mouth prevalence was the proportion of sheep immune to the disease.
Conclusion: A program of vaccination for scabby mouth will reduce the prevalence of disease during live export. However, using current technology it is not possible to deliver shipments of sheep to the Middle East that are guaranteed completely free of scabby mouth.     

Echinococcosis/hydatidosis: a severe threat in Mediterranean countries

Echinococcosis/hydatidosis is one of the most important parasitic zoonotic diseases in the world. Both cystic hydatidosis (CE) caused by Echinococcus granulosus and alveolar echinococcosis (AE) caused by E. multilocularis have been reported in several countries of the Mediterranean region (MR). E. granulosus has always been present in the MR and is the most common species. This parasite depends on the dog-sheep cycle and is actively transmitted in all pastoral regions where sheep, cattle and camelids predominate. E. multilocularis occurs only sporadically in limited areas of France, Serbia and Montenegro, Turkey, Tunisia and Morocco. However recent evidence indicates that it is spreading into other regions of the Mediterranean. Due to the lack of well-documented data, and to the fact that CE is not a notifiable disease in the majority of M countries, the precise incidence and prevalence of CE in humans and animals are not known. Published data suggests that prevalence is rather high in North Africa, Turkey, Greece, and in several regions of Italy and Spain. CE is an increasing public health and socio-economic concern due to the considerable morbidity rates that give rise to high economic losses both in the public health sector and in the livestock industry. Hospitalisation for human CE lasts from 2 weeks to more than 1 month in case of surgery. A number of factors contribute to the increase of prevalence and to the spreading of CE in the MR. These include the diversity of livestock production systems (predominantly extensive, traditional animal husbandry), small, ill-equipped and unsupervised slaughter-houses, illegal and family slaughtering, low public awareness of hydatid diseases, and the high population of stray dogs. Cyprus is the only country where an eradication programme has been successfully implemented. There have been, however, important developments in the last decade in CE epidemiology, in the diagnosis of canine infection, in strain characterisation and in immune strategies against CE in animals. This scientific progress, together with effective health education programmes, will likely improve control programmes and reduce the time required to achieve significant decreases in prevalence or eradication.     

Estimating the production losses due to cystic echinococcosis in ruminants in Turkey

The aim of this study was to estimate the production losses due to cystic echinococcosis (CE) in cattle, sheep and goats in Turkey. For this purpose, official records and previously published data in the literature were used. The weighted mean prevalence rates of the disease were calculated to be 7.4% in cattle, 46.3% in sheep and 10.9% in goats. The financial losses were estimated in US$ at 2008 current prices under expected (mean value), optimistic (mean value lowered by 10%), and pessimistic (mean value increased by 10%) scenarios. The production losses in an infected ruminant were estimated as US$ 139.2 (125.3–153.2, under optimistic–pessimistic scenarios) for cattle, US$ 13.7 (12.3–15.1) for sheep, and US$ 13.9 (12.5–15.3) for goats. The nation-wide annual losses due to CE were estimated as US$ 32.4 million (26.2–39.1) for cattle, US$ 54.1 million (43.8–65.5) for sheep and US$ 2.7 million (2.2–3.3) for goats. The nation-wide production losses due to CE in Turkey in 2008 were calculated as US$ 89.2 million (72.2–107.9). The results of this study may provide information to assist decisions of the policy makers in prioritising the allocation of scarce resources in controlling animal diseases in Turkey. However, alternative disease control-eradication programmes and cost-benefit analyses of them are needed for the future studies of this kind to provide better decision support in this area.     

Farmer reported prevalence and factors associated with contagious ovine digital dermatitis in Wales: A questionnaire of 511 sheep farmers

In 2012, 2000 questionnaires were sent to a random sample of Welsh sheep farmers. The questionnaire investigated farmers’ knowledge and views on contagious ovine digital dermatitis (CODD) – an emerging disease of sheep responsible for causing severe lameness, welfare and production problems. The overall response rate was 28.3% with a usable response rate of 25.6%. The between farm prevalence of CODD was 35.0% and the median farmer estimated prevalence of CODD was 2.0%. The disease now appears endemic and widespread in Wales. Furthermore, there has been a rapid increase in reports of CODD arriving on farms since the year 2000. Risk factors for CODD identified in this study include the presence of bovine digital dermatitis (BDD) in cattle on the farm and larger flocks. Farmers also consider concurrent footrot/interdigital dermatitis, buying in sheep, adult sheep, time of year and housing to be associated with CODD. Further experimental research is necessary to establish whether these observations are true associations.     

Sheep oestrosis (Oestrus ovis Linné 1761, Diptera: Oestridae) in Sardinia, Italy.

Oestrosis, the nasal myiasis of sheep and goats, is caused by the larvae of Oestrus ovis L. 1758 (Diptera, Oestridae) that develop from the first to the third stage larva in the nasal cavities and frontal sinuses of affected animals. The authors report the results of an epidemiological study of oestrosis of sheep in Sardinia, Italy. Heads of 6-month to 10-year-old Sardinian sheep (n=566) from 124 free-ranging flocks were examined for the presence and location O. ovis larvae from December 1996 to November 1997. Larvae were collected, counted, and larval stages were identified. O. ovis larvae were found in 100% of examined flocks and in 91% (514/566) of examined sheep. The monthly prevalence ranged from 69% in May to 100% in July. First stage larvae were found in 82% (463) of all heads examined, second stage larvae in 65% (367) and third stage larvae in 10% (56). The majority of sheep harboured first stage larvae, with prevalences of over 80% throughout most of the study period. The prevalence of O. ovis found in this study of Sardinian sheep is the highest reported in the Mediterranean area. The high percentage of first stage larvae found throughout the entire study period may be due to a brief period of decreased rate of larval maturation, in particular in December 1996 (96%) and January-October 1997 (94%). Third stage larvae were consistently present, often however, with extremely low prevalences compared to total larval burden.     

Serological patterns,antibody half-life and shedding in urine of Leptospira spp. in naturally exposed sheep

Abstract

AIMS: To determine within-farm prevalence, longitudinal pattern of exposure measured by serology, antibody titre longevity and point prevalence of shedding in urine of Leptospira borgpetersenii serovar Hardjo and L. interrogans serovar Pomona in naturally infected sheep on a sample of commercial farms in New Zealand.

METHODS: On eight commercial sheep farms, between September 2011 and January 2014, blood samples were collected from 115–217 ewe lambs on each farm, at intervals of 2–11 months. They were analysed by microscopic agglutination test (MAT) for antibodies to L. borgpetersenii serovar Hardjo and L. interrogans serovar Pomona, using a titre cut-point of 48. Urine from 98 animals was tested by quantitative PCR (qPCR). The half-life of antibodies was estimated in 185 sheep for serovar Hardjo and 21 for Pomona, and the seroprevalence and mean titre of animals lost to follow-up was compared with those remaining in the study.

RESULTS: Within-flock seroprevalence for serovar Hardjo reached a maximum at 17–22 months of age, ranging from 79 to 100%. Seroprevalence for serovar Pomona rose above 10% on three farms and increased to 21–54% by 4–14 months. Seroconversions occurred mainly from late autumn to early summer at 7–15 months of age. Seroprevalences ranging from 3 to 76% for serovar Hardjo and 0.5 to 15% for serovar Pomona were observed up to 3 months of age, likely due to maternally derived immunity. The half-life of antibody in response to infection was estimated to be 6.7 (95% CI=5.8–7.9) months for serovar Hardjo and 6.3 (95% CI=4.8–9.0) months for Pomona. The prevalence of sheep with urine positive for leptospires on qPCR on each farm ranged from 11 to 88%. All but one of the qPCR-positive animals were seropositive for serovar Hardjo. On two farms where Pomona exposure was observed, animals that were lost to follow-up had a higher geometric mean titre for serovar Pomona than those remaining in the study.

CONCLUSIONS: This study demonstrated seasonal exposure from autumn to early summer in young sheep, a wide range of within-flock serological and shedding prevalence, and gives an estimation of the half-life of MAT titres in sheep. More extensive data are needed to fully understand the epidemiology of leptospirosis in sheep flocks across New Zealand and, along with economic analysis, to justify and design cost-effective and efficient control measures to protect human and animal health.     

Serum antibodies to Dicrocoelium dendriticum in sheep from Sardinia (Italy)

An indirect enzyme-linked immunosorbent assay (ELISA) with Dicrocoelium dendriticum excretory/secretory antigens was used to evaluate the presence of serum antibodies against the trematode in 738 sheep randomly chosen in Sardinia (Italy). Coprological sedimentation was used to discover egg-output. Seropositivity was detected in 86.2% tested sheep, whereas faecal prevalence was 6.7%; all that were faecal-positive also were ELISA-positive.     

Longitudinal study of the spread of ovine Johne's disease in a sheep flock in southeastern New South Wales

OBJECTIVE: The aim of this study was to apply whole flock testing over time to determine the prevalence, distribution and spread of infection in a recently infected flock, with a view to planning intervention strategies for disease control. PROCEDURE: Serology, pooled faecal culture (PFC) and histology were used to determine the distribution and persistence of infection in a sheep flock in south east New South Wales between 1997 and 2002. Partial flock testing was done up to June 2000, after which annual whole flock testing, using PFC was performed. RESULTS: Faecal shedding of M a paratuberculosis was not detected in home-bred sheep until 7 years after the introduction of infected sheep in 1993. For at least 7 years there was clustering of infection and shedding within two age groups only. The infected groups appeared to have been exposed to infection (mycobacterial contamination) at an early age (<12 months) and commenced shedding at 5 years of age or older. Groups that were exposed to contamination as adults did not shed detectable amounts of M a paratuberculosis during the study period. CONCLUSION: Clustering of detectable infection in age groups of sheep that were exposed as lambs was a feature on this farm, providing indirect evidence of finite duration of survival of M a paratuberculosis on pasture and the influence of age on the susceptibility of sheep to develop detectable M a paratuberculosis infection. Spread of infection occurred very slowly and was probably related to the long incubation period (exposure to shedding interval) of 5 years observed on this farm. The findings suggest that partial flock culling, selective grazing management and vaccination could lead to a reduction in mycobacterial contamination on farm to a level at which patent infection no longer occurs. Better understanding of disease spread within flocks over time through flock profiling using PFC will help in devising surveillance strategies (including testing protocols for market assurance testing) to detect infected flocks where there has been clustering and slow spread of infection.     

Epidemiological study of the cystic echinococcosis in Morocco

The objectives of this epidemiological study on cystic echinococcosis (CE) in Morocco (2001-2004) were to update the prevalence of CE in different animal species living in the most important areas of the country and to collect protoscoleces and germinal layers for genetic research purposes. The post mortem inspection concerned 2948 sheep, 2337 goats, 618 cattle, 482 camels and 455 equines (325 horses, 60 mules and 70 donkeys) in five different regions: the Rif (Mediterranean coast and high mountains of the Rif), the Loukkos (Atlantic northwest plain), the center (Rabat and Casablanca regions), the Middle Atlas mountains and the south (arid and semi desert areas). The global CE infection prevalence rates obtained were 22.98% in cattle, 10.58% in sheep, 12.03% in camels, 17.80% in equines and 1.88% in goats. The infection rates were especially high in the Middle Atlas in cattle (48.72%) and in the Loukkos in cattle and sheep (37.61 and 31.65%, respectively). The majority of infected cattle (49.6%) and sheep (52.1%) had hydatid cysts in both liver and lungs. Except for cattle, the liver was more infected than lungs in all the other animal species. Animals more than 5 years old were the most infected in all species. The mean CE infection rates of these animals were about 56% in cattle, 40% in sheep, 20% in camels, 17.80% in equines and 7% in goats. These rates were much higher in the Loukkos (85% of cattle and 59% of sheep) and in the Middle Atlas (68% of cattle and 45% of sheep) than in the other regions. Results showed that Echinococcus granulosus is in an endemic steady state with no evidence of protective immunity in the intermediate hosts. The mean numbers of infections per year are 0.099 for cattle, 0.063 for sheep, 0.03 for camels and 0.010 for goats.     

A cross-sectional study to show Eperythrozoon ovis infection is prevalent in Western Australian sheep farms

A serological survey and risk factor study was conducted to estimate the prevalence of Eperythrozoon ovis infection in Western Australian weaner sheep, the prevalence of farms with infected sheep, and to identify factors affecting initiation and maintenance of infection on the farm. The study was conducted on 91 farms, purposively chosen from 41 randomly selected regional shires stratified by sheep number and rainfall zones. Twenty sheep were selected systematically from a mixed-sex flock on each farm and tested for serum antibody to E ovis using an enzyme-linked immunosorbent assay. Information on putative risk factors was collected using an interview questionnaire. Antibody to E ovis was detected in 4.5% of sheep on 47% of the farms sampled. The prevalence of E ovis infection in sheep was estimated at the 95% confidence level to be between 3.6 and 5.5%, and the prevalence of farms with infected sheep was estimated to be between 37.5 and 56.5%. Most farms with serological evidence of infection occurred in the Great Southern agricultural region (79.5%), south-east of Perth through to Albany (latitude 32 to 34 degrees S, longitude 116 to 120 degrees E), and in the Northern region (12.8%) surrounding Geraldton (latitude 29 degrees S, longitude 114 degrees E). There were significantly more farms (P less than 0.05) with evidence of infection in the Great Southern region compared to the Central region between Geraldton and Perth, and on farms in the region south compared to north of latitude 32 degrees S. None of the putative risk factors examined in the questionnaire were associated with serological evidence of infection on the farm.(ABSTRACT TRUNCATED AT 250 WORDS)     

Epidemiological survey of cestode-larva disease in Greek sheep flocks

The epidemiological status of hydatidosis, cysticercosis, and gid in sheep and the production practices of sheep farmers that increase the risk of exposure of sheep to infecting agents of these diseases were investigated in Thessaly, central Greece during 2002-2006. A total of 700 hoggets (sheep up to the age of 1 year) and 1500 adult sheep were examined randomly at an abattoir survey and the prevalences of hydatidosis and cysticercosis were found 39.32% and 29.41%, respectively. Hoggets had significantly lower prevalences of hydatidosis and cysticercosis compared to adult sheep (p<0.001). The distribution of parasitic cysts showed an overdispersion pattern mostly in the hogget population. The proportion of fertile hydatid cysts was significantly higher in hoggets compared to adult sheep (p<0.001). A cohort of 74 sheep flocks was observed during the same period in a prospective survey to assess the incidence of gid. A total of 57 sheep belonging to 15 flocks (20.27% of investigated flocks) developed clinical signs of gid at an annual rate of 11.40+/-4.77 (95% C.I.). In the infected flocks there were 3.80+/-0.92 (95% C.I.) gid cases per flock. The mean age of onset of clinical signs for all sheep was 11.86+/-1.33 months (95% C.I.) (range 5-22 months) while for hoggets was 8.48+/-0.73 (95% C.I.) (range 5-12 months) and for adult sheep 17.23+/-1.42 (95% C.I.) (range 13-22 months). A significant difference was observed in the prevalence of unilateral blindness between hoggets (31.42%) and adult sheep (4.54%) (p<0.05). The most common production practices identified in a questionnaire survey of sheep farmers that may increase the risk of exposure of sheep to hydatidosis, cysticercosis, and gid were the improper disposal of dead animals, the access of farm dogs to offal of slaughtered sheep, the carelessness of farmers to treat farm dogs with anthelmintics, and the grazing of flocks in fields where stray dogs have free access.