Diagnosis of canine echinococcosis: comparison of coproantigen detection with necropsy in stray dogs and red foxes from northern Jordan

The sandwich enzyme linked immunosorbent assay (ELISA) was used as a diagnostic test for Echinococcus granulosus infection by detecting coproantigens in 94 stray dogs Canis familiaris and eight red foxes (Vulpes vulpes) from northern Jordan. The results were analyzed in relation to actual helminth infection as revealed by necropsy. The infection rate of dogs with E. granulosus was 13.8% with a worm load ranging between 3-> 10,000 per infected dog. In contrast, eight of 13 E. granulosus infected dogs were coproantigen positive (overall sensitivity 61.5%). The sensitivity increased to 87.5% and 100% in dogs harboring > 20 and > 100 worms/dog, respectively. The specificity of coproantigen-ELISA was 91%. The greatest cross-reactivity was found in dogs infected with Dipylidium caninum. The positive and negative predictive values for the coproantigen-ELISA test were 50% and 94.2%, respectively. Thus, a coproantigen negative dog is most probably truly negative for E. granulosus. In contrast, a coproantigen positive dog may not be truly positive for E. granulosus, except if it has a high worm burden of > 100 worms/animal.     

Coproantigen detection in dogs experimentally and naturally infected with Echinococcus granulosus by a monoclonal antibody-based enzyme-linked immunosorbent assay

A sandwich ELISA for the detection of Echinococcus granulosus coproantigen in formalin and heat-treated faecal supernatants of dogs was developed. The assay used affinity-purified polyclonal antibodies obtained from rabbits hyperimmunised with E. granulosus excretory/secretory antigens and biotiaylated monoclonal antibody EmA9 produced against adult E. multilocularis somatic extract. The test was sensitive to 7 ng and 2.3 ng of E. granulosus protein and carbohydrate/ml of faecal supernatant, respectively. Thirteen helminth-free dogs were infected with different amounts of E. granulosus protoscoleces and the presence of coproantigen was monitored during the prepatent period until day 35 post-infection, when they were necropsied. Faecal antigen levels started to rise above the normal range between days 10 and 20 post-infection, and typically peaked at the end of the experiment. All the dogs, bearing from 3 to 67 700 worms, showed positive values in the ELISA during the prepatent period. One dog experimentally infected with Taenia hydatigena metacestode and harbouring three worms, tested positive only after the prepatent period at day 52. The test was applied to 98 stray dogs. The ELISA detected all of four dogs naturally infected with E. granulosus, two dogs with patent infections of T. hydatigena and two dogs with no cestode infections, sbowing a sensitivity of 100% and a specificity of 96%.     

Serological and molecular studies on Dirofilaria immitis in dogs from Turkey

We estimated the prevalence of Dirofilaria immitis infection in domestic dogs in five Turkish provinces - Sakarya, Kocaeli, Ankara, Elazig and Mersin - using a commercial ELISA kit for detecting circulating antigen and a PCR test for detecting circulating microfilarial DNA. A total of 211 whole-blood and serum samples were collected from dogs of various breeds, ages and life status (owned or stray). Sample population characteristics were recorded and examined for differences in prevalence. Additionally, we collected 15 blood samples from cats (14 owned and 1 stray) from Ankara province and used PCR to detect D. immitis infection. Twenty-seven (12.8%) of 211 dog samples were positive for D. immitis antigen by ELISA. No differences in prevalence were observed by sex (female: 14.4%; male: 10.7%; P>0.05). The prevalence of D. immitis infection varied with age: 11.8% in younger dogs (0.5-2 years) and 17.5% in older dogs (3-5 years). Prevalence between stray dogs (15.2%) and owned dogs (9.3%) did not differ (P>0.05). Prevalence rates were highest in Kocaeli province (18.3%), followed by Ankara (14.8%), Sakarya (12.3%) and Mersin (10.5%) provinces. Prevalence in Elazig province was 0%. No dogs or cats had microfilarial DNA detectable by PCR.     

Vectorial competence of Aedes aegypti (Linnaeus 1762) Rio de Janeiro strain, to Dirofilaria immitis (Leidy 1856)

Dirofilaria immitis (Leidy 1856), a nematode parasite, is the etiologic agent of canine heartworm disease and mosquitoes are essential intermediate hosts. Mosquito susceptibility to the worms differ with species, strains and also among individuals of the same strain. To evaluate the degree of susceptibility of Rio de Janeiro laboratory raised strain of Aedes aegypti, we fed mosquitoes on canine blood with different densities of microfilariae (mf). There was no significant difference in the rate of development among the three different densities of mf. Infective larvae were found in the head and proboscis of all mosquitoes provided bloodmeals with different densities of mf after the 11th day post-infection. The infection rate of mosquitoes after ingestion of blood containing 3,000 mf/ml, 5,000 mf/ml and 7,000 mf/ml were 55.3%, 66.7% and 100%, respectively. The vector efficiency indices ranged from 1.6 to 9.3. The finding of L3 stage larvae, high infection rates and vector efficiency indices suggest that Ae. aegypti, Rio de Janeiro laboratory strain, is a potential vector of D. immitis, although of low efficiency.     

Impact of Three Rounds of Mass Drug Administration on Lymphatic Filariasis in Areas Previously Treated for Onchocerciasis in Sierra Leone

Background

1974–2005 studies across Sierra Leone showed onchocerciasis endemicity in 12 of 14 health districts (HDs) and baseline studies 2005–2008 showed lymphatic filariasis (LF) endemicity in all 14 HDs. Three integrated annual mass drug administration (MDA) were conducted in the 12 co-endemic districts 2008–2010 with good geographic, programme and drug coverage. Midterm assessment was conducted 2011 to determine impact of these MDAs on LF in these districts.

Methodology/Principal Findings

The mf prevalence and intensity in the 12 districts were determined using the thick blood film method and results compared with baseline data from 2007–2008. Overall mf prevalence fell from 2.6% (95% CI: 2.3%–3.0%) to 0.3% (95% CI: 0.19%–0.47%), a decrease of 88.5% (p = 0.000); prevalence was 0.0% (100.0% decrease) in four districts: Bo, Moyamba, Kenema and Kono (p = 0.001, 0.025, 0.085 and 0.000 respectively); and seven districts had reductions in mf prevalence of between 70.0% and 95.0% (p = 0.000, 0.060, 0.001, 0.014, 0.000, 0.000 and 0.002 for Bombali, Bonthe, Kailahun, Kambia, Koinadugu, Port Loko and Tonkolili districts respectively). Pujehun had baseline mf prevalence of 0.0%, which was maintained. Only Bombali still had an mf prevalence ≥1.0% (1.58%, 95% CI: 0.80%–3.09%)), and this is the district that had the highest baseline mf prevalence: 6.9% (95% CI: 5.3%–8.8%). Overall arithmetic mean mf density after three MDAs was 17.59 mf/ml (95% CI: 15.64 mf/ml–19.55 mf/ml) among mf positive individuals (65.4% decrease from baseline of 50.9 mf/ml (95% CI: 40.25 mf/ml–61.62 mf/ml; p = 0.001) and 0.05 mf/ml (95% CI: 0.03 mf/ml–0.08 mf/ml) for the entire population examined (96.2% decrease from baseline of 1.32 mf/ml (95% CI: 1.00 mf/ml–1.65 mf/ml; p = 0.000)).

Conclusions/Significance

The results show that mf prevalence decreased to <1.0% in all but one of the 12 districts after three MDAs. Overall mf density reduced by 65.0% among mf-positive individuals, and 95.8% for the entire population.     

Onchocerciasis in British cattle: a study of Onchocerca gutturosa and O. lienalis in North Wales

Onchocerca gutturosa and O. lienalis infections in British cattle were studied by examination of cattle post-mortem originating from North Wales and Cheshire (north west England). In 463 adult animals, the microfilarial (mf) prevalence was 28.5%. In 95.3% of the mf infected animals, gravid worms could not be found at either the ligamentum nuchae or the gastro-splenic omentum. Dermal mf at the head were identified as O. gutturosa on the basis of their highly significant association with the presence of gravid O. gutturosa at the ligamentum nuchae, which were found in only 3.2% of cattle. Mfs were isolated from different skin sites and from adult worms and a minimum of 10 mfs from each isolate were examined for width and acid phosphatase (AP) staining pattern. The width of O. gutturosa dermal mf was less than 4 micron (4 isolations), narrower than that of putative O. lienalis mf isolated from umbilical skin of cattle without evidence of O. gutturosa, which were in 20/22 isolations greater than 4 micron wide. The dermal mf were also distinguished on the basis of different AP staining patterns which, for each species, correlated closely with that of hatched intrauterine mf from their respective adult female worms. Based on the criteria of morphology and AP staining patterns the mf species prevalences in the survey population were estimated as O. lienalis 24.1% and O. gutturosa 2.2%, with a further 2.2% of cattle infected with both species. The results indicate that the predilection site of adult O. lienalis is not the gastro-splenic omentum. In North Wales, the distribution of the two species was different; O. lienalis was widely distributed in all cattle rearing areas both lowland and upland, whereas O. gutturosa was largely restricted to valleys close to major rivers.     

Estimation of different degrees of provocation by DEC (diethyl carbamazine citrate) medication in bancroftian filariasis in Vellore, Tamilnadu

DEC in general has the power to bringout the filarial worms into the peripheral blood when administered. The provocative effect was observed in 86.8% of the mf positive cases. Optimum provocative effect was noticed in the age group above 12 years and there was no influence on sex. The maximum effect of provocation was seen at 60 min after the administration 2 mg/kg body weight DEC. The mf rate was high in the blood collected after the administration of DEC during day time, than that during night.     

Detection of Helminth Eggs and Identification of Hookworm Species in Stray Cats,Dogs and Soil from Klang Valley,Malaysia

The present study was conducted to determine the prevalence of helminth eggs excreted in the faeces of stray cats, dogs and in soil samples. A total of 505 fresh samples of faeces (from 227 dogs and 152 cats) and soil were collected. The egg stage was detected via microscopy after the application of formalin–ether concentration technique. Genomic DNA was extracted from the samples containing hookworm eggs and used for further identification to the species level using real-time polymerase chain reaction coupled with high resolution melting analysis. Microscopic observation showed that the overall prevalence of helminth eggs among stray cats and dogs was 75.7% (95% CI = 71.2%–79.9%), in which 87.7% of dogs and 57.9% of cats were infected with at least one parasite genus. Five genera of heliminth eggs were detected in the faecal samples, including hookworms (46.4%), Toxocara (11.1%), Trichuris (8.4%), Spirometra (7.4%) and Ascaris (2.4%). The prevalence of helminth infections among stray dogs was significantly higher than that among stray cats (p < 0.001). Only three genera of helminths were detected in soil samples with the prevalence of 23% (95% CI = 15.1%–31%), consisting of hookworms (16.6%), Ascaris (4%) and Toxocara (2.4%). The molecular identification of hookworm species revealed that Ancylostoma ceylanicum was dominant in both faecal and soil samples. The dog hookworm, Ancylostoma caninum, was also detected among cats, which is the first such occurrence reported in Malaysia till date. This finding indicated that there was a cross-infection of A. caninum between stray cats and dogs because of their coexistent within human communities. Taken together, these data suggest the potential role of stray cats and dogs as being the main sources of environmental contamination as well as for human infections.     

Experimental infection of Dirofilaria immitis in raccoon dogs

Canine heartworm (Dirofilaria immitis) is a nematode that naturally parasitizes in the pulmonary arteries and the right ventricle of domestic dogs (Canis familiaris) as final hosts. Japanese raccoon dogs (Nyctereutes procyonoides viverrinus) also are known to be susceptible to infection by the parasite. However, prevalence of this infection among free-ranging raccoon dogs is low and so is the worm burden. To examine the susceptibility of the raccoon dog to D. immitis infection, 3 raccoon dogs and 2 beagles were inoculated 4 times with 25 third-stage larvae (L3s) of D. immitis at 3-wk intervals. Worms were recovered from 2 raccoon dogs and both domestic dogs. The average percentage of recovery (2.3%) of the raccoon dogs was almost 10 times lower (24.5%) than that of the domestic dogs, but there was no significant difference in the body length of worms recovered from 2 types of hosts. To examine microfilaremia, 2 raccoon dogs were infected with 100 L3s. Microfilaremia was observed for 180 days postinoculation (PI) but disappeared at about 300 days PI. The raccoon dog was mildly susceptible to infection with D. immitis, but surviving worms developed and matured normally.     

Assessment of loiasis and outcomes of ivermectin masstreatment in Ijebu-North, Nigeria

A total of 286 individuals from 3 selected communities (Areedi-Aje, Ipakodo/Ojokodo, and Ijebu-Igbo) of Ijebu-North, southwestern Nigeria were examined for Loa loa microfilaremia using finger prick blood smear, between December 2008 and March 2009. Rapid assessment procedure for loiasis (RAPLOA) was used to obtain information, from 187 Ijebu-Igbo residents, on adverse reactions experienced from retrospective treatments with ivermectin and history of eye worm. Only 33.9% of the respondents reported having had a history of eye worm while 33.2% had microfilaremia. The demographic factor of gender was not significant determinants of the prevalence (P>0.05) while age was significant (P<0.05). The highest prevalence of eye worm history and microfilaremia were recorded in 61-70 and 15-20 years of age categories, respectively. Ijebu-Igbo had 27.3% eye worm history, 32.1% microfilaremia, and the highest intensity of 140 microfilariae (mf)/ml. Ipakodo area had the highest eye worm history of 54.4% and the highest intensity of 420 mf/ml. Areedi-Aje had the highest occurrence of 45.2% microfilaremia and the highest intensity of 460 mf/ml. Predictably, Areedi-Aje and Ipakodo areas were high risk communities. The low intensity of L. loa infection with an insignificant (2.1%; P>0.05) adverse reactions from 187 subjects involved in the retrospective ivermectin administration confirmed that ivermectin delivery may be considered safe. The community-directed treatment with ivermectin (CDTI) programme was most probably responsible for the low prevalence and intensity.     

Setaria digitata infections in cattle: parasite load, microfilaraemia status and relationship to immune response

A total of 110 cattle were examined in an area endemic for Bancroftian filariasis for the prevalence of infection of the bovine filarial parasite Setaria digitata. About 12.5% of cattle were found to harbour both adult worms in the peritoneum and microfilariae (mf) in circulation; 70% of the cattle were amicrofilaraemic but with an adult worm infection. A third group of cattle (16.5%) was free of detectable mf and adult worms. The presence of adult worms and/or mf did not influence the antibody levels to any of the four antigen preparations of S. digitata. However, there was a significant inverse relationship between the presence of antibodies to microfilarial sheaths and the absence of circulating mf as shown by the immunoperoxidase assay. Cattle immunoglobulin containing high titres of anti-sheath antibodies cleared circulating microfilariae very effectively in Mastomys coucha thus demonstrating the protective nature of anti-sheath antibodies in eliminating circulating microfilariae in vivo.     

First epidemiological study on exposure to Neospora caninum in different canine populations in the Algiers District (Algeria)

Neospora caninum is an important cause of abortion in cattle worldwide. Dogs act as final hosts shedding oocysts in the environment. They can also harbour the extraintestinal stage of the parasite and this may be associated with a fairly rare neuromuscular condition. The sera of 781 dogs from the Algiers District were screened by IFAT for the presence of anti-N. caninum antibodies. These dogs were distributed into four populations: local stray dogs, police dogs, dogs from breeding kennels and farm dogs. The overall seroprevalence was 21.90%. Significant differences were observed between the different populations, the highest prevalence being observed in farm (44.44%) and stray dogs (22.55%). Additionally, the highest titres were observed in farm dogs. Among studied epidemiological parameters, breed, dog origin, season and vaccination status were significantly associated with IFAT results. Additionally, a recently described real time PCR was used on the blood of 100 pound dogs and the results were compared with the serological data. A higher proportion of dogs was found to be positive by PCR when compared to the IFAT results. There was only a fairly low agreement between PCR and IFAT results which suggests that these techniques measured different aspects of the host–parasite relationship. This study indicates that the level of exposure of the canine population of Algiers area to N. caninum is very high. This would indicate a potentially high risk for N. caninum induced abortion in cattle in this region and in Algeria.     

Dog keeping in Taiwan: its contribution to the problem of free-roaming dogs

This study conducted a quantitative ethnographic analysis of the influence of demographic factors and early experience (childhood exposure to dogs) on Taiwanese dog-keeping practices and behavior. A telephone survey of a randomly selected sample of 2,001 Taiwan residents determined their dog ownership histories, current patterns of dog ownership and disposal, and other dog-related activities. The results suggest that low rates of neutering, easy availability of low- or no-cost puppies, a tendency to allow owned dogs free access to the outdoors, unrealistic expectations of dog ownership, canine behavioral problems, and religious and cultural taboos against euthanasia and shelter relinquishment have contributed to the recent increase in the numbers of free-roaming dogs in Taiwan. Logistic regression analyses determined that a relatively small number of demographic and experiential variables predicted dog ownership and disposal patterns. The most important of these was childhood experience of living with household dogs. In light of these findings, future efforts to reduce the stray dog problem should focus on enforcing registration fees, particularly for unsterilized animals; low-cost neutering schemes; and educational programs designed to promote neutering, improve knowledge of canine behavior and behavior problems, and develop more realistic expectations and attitudes toward dog ownership. Marked Taiwanese resistance to canine euthanasia and shelter relinquishment suggests a need for alternative methods of managing the existing free-roaming dog population.     

Experimental infection of Paragonimus iloktsuenensis to albino rats, dogs and cats

This study was performed to observe the susceptibility of dogs and cats as definitive hosts of Paragonimus iloktsuenensis. The metacercariae of this fluke were obtained from Sesarma dehaani collected at a focus near the mouth of Sumjin river in November, 1986 and February, 1987. The larvae isolated from the crabs were introduced per os into 7 albino rats, 2 dogs and 3 cats. The adults were recovered from the experimental animals, and they were morphologically observed and measured. The results were as follows: 1. The recovery rate of adult worms at 42 days after infection was 53.3% from three albino rats, 21.0% from a dog and 12.7% from two cats. Most of the worms were recovered from the worm capsules in the lungs. 2. The size of worms recovered from albino rats, a dog, and cats 42 days after infection averaged 6.3 x 3.2 mm, 6.3 x 3.0 mm, or 6.2 x 3.5 mm, respectively. There were little differences in the morphology of worms by different experimental animals. 3. The size of eggs from a dog was 88.9 x 49.3 microns, and that from cats was 84.3 x 53.7 microns on average. Dogs and cats were good definitive hosts of P. iloktsuenensis. This fact suggests that human infection by this fluke may be possible if the metacercariae were ingested.     

Efficacy of ivermectin in hookworms as examined in Ancylostoma caninum infections

Single oral doses of ivermectin were given to dogs with moderate or heavy infections of Ancylostoma caninum (egg counts ranging from 7,100 to 41,700 eggs/g feces) at 100, 50, 30, or 10 micrograms/kg body weight. Each of these dosages was effective in clearing the infection completely, so that numerous worms were passed in the feces on days 1-3, but no worm was recovered from the intestinal tract at necropsy on day 4 after treatment. In contrast, an average of 178 worms per dog was recovered at necropsy from the vehicle-treated control and the untreated animals. Albendazole, a known anti-hookworm agent, even in a dose of 400 mg, eliminated only 21-65% of the worms harbored by the infected animals. No untoward reaction to ivermectin or significant pathological change was noted in the experimental animals. In vitro experiments demonstrated that ivermectin: (1) was highly detrimental to actively motile adult worms in concentrations greater than 5.60 micrograms/ml; (2) was detrimental to eggs inside the uterine tissue of female worms in dosages at or greater than 10 micrograms/kg body weight; and (3) killed infected larvae in concentrations as low as 0.0025 micrograms/ml.     

Molecular survey of canine vector-borne diseases in stray dogs in Thailand

Despite the large population of stray dogs in Thailand, there is limited information on the prevalence of canine vector-borne diseases (CVBDs). In this study, a molecular survey was conducted to determine the prevalence of Babesia spp., Ehrlichia canis, Hepatozoon spp., Anaplasma platys and Mycoplasma spp. in dogs in Thailand. Of the 181 dog blood samples tested by PCR, 78/181 (43.1%) were found to be infected with one or more pathogens. The overall prevalence rates of Mycoplasma spp., Hepatozoon spp., Babesia spp., A. platys and E. canis infections were 19.9%, 18.8%, 9.4%, 4.4% and 3.9%, respectively. To the authors' knowledge, this is the first report of Mycoplasma infection in Thailand in dogs. The current findings are important for future surveillance of CVBDs and designing appropriate approaches for diagnosis and control for the diseases in Thailand.     

Canine heartworm in the domestic and wild canids of southeastern Nebraska

The prevalence of canine heartworm (Dirofilaria immitis) was examined in the domestic dog, coyote (Canis latrans), and red fox (Vulpes fulva) populations of southeastern Nebraska. Microfilariae were detected in 21.4% (22 of 103) of the domestic dogs. The average age of infection for dogs was 5.8 yr. Nine of the 22 infected dogs also were positive for Dipetalonema reconditum. Thirty-nine of 443 (8.9%) coyotes were found to have adult heartworms. The average number of male and female worms per heart was 3.7 and 3.9, respectively. The mean age of infected coyotes was 3.6 yr. Red foxes had an infection rate of 4.8% (1 of 21). This fox heart had only 1 immature female worm. A mail survey of 6 veterinary clinics was also conducted. Veterinarians reported infection rates of 0% to 18.8% in domestic dogs for their localities.     

Effect of host sex and litter on the population dynamics of Echinococcus granulosus in dogs.

Twenty-one Beagle dogs consisting of 10 males and 11 females and belonging to 3 litters were infected with 60,000 E. granulosus protoscolices each. They were killed on day 40, the parasites from their intestines recovered, and the number of worms, average number of proglottides per worm, average length per worm, percentage of worms with a uterine cavity, and percentage of egg-bearing worms were determined for each dog and analyzed per sex and litter. On average, the dogs had 1,253 +/- 339 worms (means +/- standard error) with 2.42 +/- 0.1 proglottides, were 1.59 +/- 0.07 mm long, and 25.6 +/- 4.8% of the worms presented a uterine cavity and 1.2 +/- 0.6% bore eggs. The number of worms exhibited a bimodal distribution with 19 dogs having less than or equal to 2,565 worms and 2 greater than or equal to 5,520 worms. Average number of proglottides also showed a bimodal distribution with 7 dogs having less than or equal to 2.1 proglottides per worm and 14 dogs having greater than or equal to 2.4 proglottides per worm. The parasites were significantly more numerous in females than in the males (1,964 +/- 573 vs. 681 +/- 202), had more proglottides (2.67 +/- 0.08 vs. 2.15 +/- 0.16), and were longer (1.72 +/- 0.07 vs. 1.44 +/- 0.11 mm). The percentages of parasites with a uterine cavity (27.8 +/- 5.9 vs. 23.2 +/- 8.1) or bearing eggs (1.0 +/- 0.5 vs. 1.5 +/- 1.8) were comparable in females and males.(ABSTRACT TRUNCATED AT 250 WORDS)     

Modeling the transmission of Echinococcus granulosus and Echinococcus multilocularis in dogs for a high endemic region of the Tibetan plateau

Echinococcus granulosus and Echinococcus multilocularis abundance and prevalence data, for domestic dogs of Shiqu County, Sichuan Province, People's Republic of China, were fitted to mathematical models to evaluate transmission parameters. Abundance models, assuming the presence and absence of immunity, were fit for both E. granulosus and E. multilocularis using Bayesian priors, maximum likelihood, and Monte Carlo sampling techniques. When the models were compared, using the likelihood ratio test for nested models, the model assuming the presence of immunity was the best fit for E. granulosus infection, with a purgation based prevalence of 8% (true prevalence interval of 8-19% based on the sensitivity of purgation) and a mean abundance of 80 parasites per dog, with an average infection pressure of 560 parasites per year. In contrast, the model assuming the absence of immunity was the best fit for E. multilocularis infection, with a purgation based prevalence of 12% (true prevalence interval of 13-33% based on the sensitivity of purgation) and a mean abundance of 131 parasites per dog, with an average infection pressure of 334 or 533 parasites per year assuming a 5 or 3 month parasite life expectancy, respectively. The prevalence data for both parasites was then fit to a set of differential equations modeling the transition between infection states in order to determine number of infectious insults per year. Infection pressure was 0.21, with a 95% credibility interval of 0.12 to 0.41, infections per year for E. granulosus and 0.52, with a 95% credibility interval of 0.29-0.77, infections per year for E. multilocularis assuming a 5 month parasite lifespan or 0.85, with a 95% credibility interval of 0.47-1.25 infections per year, assuming a 3 month E. multilocularis lifespan in dogs.     

Epidemiology of Echinococcus granulosus in Arbil province, northern Iraq, 1990-1998

During the period 1990-1998, 99 cases of human cystic hydatidosis (12.4 cases per year) were surgically treated at the two main hospitals in Arbil province, northern Iraq, and from this the human occurence for the province was estimated to be 2 per 100,000 inhabitants. In the same area, 1270 sheep, 550 goats and 320 cattle were examined at slaughter for hydatid cysts and prevalence rates were found to be 15.0%, 6.2% and 10.9%, respectively. A decreasing tendency in livestock prevalences was found towards the end of the study period. As in humans, most of the hydatid cysts in livestock were located in the liver. Fertility of sheep cysts, i.e. those containing protoscoleces, was found to be significantly higher (64%) than that of goats (35.7%) and cattle (29.8%). The percentage of fertile cysts containing viable protoscoleces varied between 63 and 82% in the livers and between 72 and 79% in the lungs of the different animal species. A total of 97 stray dogs were examined post-mortem in the years 1991, 1992 and 1998, and Echinococcus granulosus worms were found in the intestines of 48 dogs (49.5%). High worm burdens (> 1000) were observed in 37% of the dogs, medium worm burdens (200-1000) in 41%, and low worm burdens (< 200) in 22%. In 1998, the prevalence of canine echinococcosis (24.3%) was found to be significantly lower than in 1991 (70.4%) and 1992 (60.6%). The prevalence of human hydatidosis did not differ significantly over the years, but the study confirmed that hydatidosis is endemic in northern Iraq, and that housewives, labourers and farmers appear to be at the greatest risk of infection.