An extensive ultrasound and serologic study to investigate the prevalence of human cystic echinococcosis in northern Libya.

A prevalence study of abdominal cystic echinococcosis (CE) was undertaken in the northwest, north-central, and northeast regions of Libya. A total of 36 villages along the coast were included, in which 20,220 people were screened by portable ultrasound. Three hundred thirty-nine (1.7%) were diagnosed with CE. There was no significant difference between CE prevalence rates in the three regions of Libya (mean = 1.6%); however, intervillage rates were variable, ranging from 0% to 4.5%. The prevalence of CE increased significantly with age (P < 0.0001) and females were significantly more affected (2%) than males (1.3%) (P < 0.0001). Cases of CE were distributed among 3.2% of housewives, 2.6% of farmers, 2.3% of male civil servants, 1.3% of female students, and 1.1% of male students. Housewives (P < 0.0001) and students (P < 0.0001) were significantly more at risk for CE. A statistically significant proportion (62% [210 of 339]) of CE cases kept dogs (P < 0.0001). Of the ultrasound-positive CE cases 69% (233 of 339) were antibody seropositive by ELISA using Echinococcus granulosus hydatid cyst fluid antigen B. Blood samples (n = 10,096) collected onto filter papers were taken randomly from ultrasound-negative people who entered the study, of which 11.2% were found to be seropositive. Seropositivity increased with age (P < 0.0001), with females exhibiting higher seroprevalence than males for all age groups (P < 0.0001). Seroprevalence was distributed occupationally among 17.3% of female students, 11.2% of male students, 8.3% of housewives, 7.3% of farmers, and 6.4% of male civil servants. Housewives and students were more likely to be seropositive (P < 0.0001). Forty-seven percent (526) of the seroreactors kept dogs. All liver hydatid cysts detected by ultrasound during community screening were classified according to morphology and size into six types. Type I (17.5% of all cases) were small univesicular cysts less than 50 mm in diameter with no laminations or daughter cysts. Type II (34%) were univesicular cysts with only laminations. Type IIIa (8.5%) were univesicular cysts with the appearance of laminations and daughter cysts. Type IIIb (13%) were univesicular with laminations and less prominent daughter cysts. Type IV (5.6%) presented as a solid mass. Type V were degenerated calcified or partially calcified cysts (13.2%). Type VI presented as multiple cysts (8% of all cases). The CE cases that exhibited Types II, IIIa, IIIb, IV or VI cysts showed the highest seropositivity (86%, 96%, 95%, 100%, and 96%, respectively), while Types I and V were the least seroreactive (38% and 22%, respectively). Cases of CE occurred in 311 families, with 93% having only one member as a CE case while 7% of the families had two or more cases. However, 25% of the ultrasound-negative persons belonging to families with an index CE case were seropositive for antibodies to Echinococcus. These results confirm the importance of human CE in Libya. They also confirm the usefulness of ultrasound combined with serology as a mass screening approach for CE in north African communities.

Immunoblot evaluation of the 100 and 130 kDa antigens in camel hydatid cyst fluid for the serodiagnosis of human cystic echinococcosis in Libya.

Two high molecular weight antigens with molecular masses approximately 100 kDa and 130 kDa were identified by immunoblotting camel hydatid cyst fluid, with 94% sensitivity in sera from surgically confirmed Libyan cystic echinococcosis cases. 40% of sera from surgically confirmed alveolar echinococcosis cases cross-reacted with the 100 and 130 kDa antigens, as did 5.3% of sera from human Taenia solium cysticercosis patients. No cross-reaction occurred with sera from human schistosomiasis mansoni or onchocerciasis patients. In addition, all sera from patients with non-hydatid space-occupying lesions (i.e. simple liver cysts, kidney cysts, lung tuberculosis, pulmonary carcinoma, pulmonary empyema, and lung abscess) were seronegative against the same antigens, as were control serum samples from healthy individuals. The 100 and 130 kDa antigens were strongly recognized by sera from cystic echinococcosis patients when camel or horse hydatid cyst fluid was used in immunoblotting but were only weakly recognized if sheep or human hydatid cyst fluid was used. Camel hydatid cyst fluid could be an important source of diagnostic antigens for human cystic echinococcosis in the Middle East endemic region.

Phoretic and parasitic mites infesting the New World screwworm fly, Cochliomyia hominivorax, following sterile insect releases in Libya.

During the screwworm eradication programme in Libya in 1991, trapped specimens of Cochliomyia hominivorax (Coquerel) were found infested with phoretic mites, Macrocheles muscaedomesticae (Scopoli), or parasitic mites, Trichotromidium muscarum (Riley). The possible sources of infestation and potential effects of mites on screwworm flies are discussed.

Experimental infection of Libyan sheep with Echinococcus granulosus.

The growth rate of unilocular hydatid cysts over a two-year period was studied in Libyan sheep dosed orally with gravid segments of Echinococcus granulosus taken from stray town dogs. Seven of the eight sheep dosed with 20-100 gravid segments (say 4000-20,000 eggs) had developed only infertile hydatid cysts after 107-611 days. Sheep dosed with 1000 gravid segments (say 200,000 eggs) had developed only sterile cysts when examined 358 days after dosing. Fertile cysts were recovered from the lungs after 428 days, and after 584 days from the liver. Only sterile cysts were seen in the heart, spleen and kidneys.

Echinococcosis in Libya. III. Further studies on the prevalence of Echinococcus granulosus in dogs.

Of 92 dogs examined for Echinococcus granulosus at five sites in Libya from April 1985 to September 1988 33 (35.9%) were infected, the prevalences ranging from 60% (Zawiyah) and 52.0% (Tripoli) in the north-west, to 28.6% (Benghazi) and 28.5% (Darna) in the north-east. None of eight dogs at Al-Kufra, in the south-eastern desert, were infected. Twenty dogs each had two to 200 worms, nine had 201-1000 worms and four each had over 1000 worms (one dog in Tripoli had 17,120 worms). Most infections were seen in dogs aged three to four years; 45.4% of bitches and 35.4% of males were infected.

Echinococcosis in Libya. IV. Prevalence of hydatidosis (Echinococcus granulosus) in goats, cattle and camels.

During a survey of 14 Libyan abattoirs in 1985-1987 the carcasses of 4316 locally-bred goats, cattle and camels were inspected for cysts of Echinococcus granulosus. Of 2295 goats, 35 adults (1.5%) had cysts; no kids were infected. Thirty-one adult goats had infected livers, 28 had lung infections, and four each had cysts in their kidneys and spleens. Most (59.7%) of the infections were light, with medium infections in 31.3% and heavy infections in 8.9%; 85.7% of the cysts in the lungs and 38.7% of those in the livers were fertile; three of the four kidney infections and two of the four spleen infections were fertile. Of the 1023 cattle carcasses, mild infections with E. granulosus were seen in 55 (5.4%); all the cysts were sterile and confined to the liver. Of 998 camels, 358 (35.9%) had hydatid cysts. These involved the lungs in 96.9%, either as the sole site (74.3%) or jointly with the liver (22.6%). Lung cysts (57.6%) and liver cysts (41.2%) were fertile.

The screwworm fly in Libya: a threat to the livestock industry of the Old World.

The screwworm fly, Cochliomyia hominivorax (Coquerel), is the most serious insect pest of cattle in the New World. It has recently been recorded in Libya, where it appears to have become established. This article documents these recent finds, and provides background information on the recognition of the fly, its biology, distribution and importance.

Echinococcosis in Libya. I. Prevalence of Echinococcus granulosus in dogs with particular reference to the role of the dog in Libyan society.

Of 151 dogs examined in 14 localities in Libya, 42 (27.81%) were infected with Echinococcus granulosus. The prevalence of the worms was generally higher in the coastal areas. Infections were light (1-200 worms) in 24 of the infected dogs, medium (201-1000 worms) in ten and high (over 1000 worms) in eight. The maximum number of worms was 12,821, recorded in a four-year-old dog. Infection rates differed with age: 12.5% in dogs aged up to one year, 36.6% for one to two years, 19.3% for two to three years, 44.2% for three to four years and 14.3% for dogs aged over five years. The role of dogs in Libyan society is discussed.

Echinococcosis in Libya. II. Prevalence of hydatidosis (Echinococcus granulosus) in sheep.

The incidence and geographical distribution of hydatidosis was examined in sheep from ten localities in Libya. A total of 402 cases of hydatid disease (7.85%) were confirmed in a total of 5118 sheep examined; 12.74% of adult sheep were infected, but only 0.29% of lambs. The liver was the organ most commonly infected (97.26% of all infections), followed by the lungs (58.70%), kidneys (1.76%), spleen (0.74%) and heart, mesentery and muscles (0.24% each). The intensity of infection varied from one to more than ten fertile or sterile cysts. Infections were light in 43.73% of livers and 47.03% of lungs, medium in 33.24% of livers and 42.79% of lungs, heavy in 13.55% of livers and 7.62% of lungs, and very heavy in 9.96% of livers and 2.54% of lungs. A total of 73.13% of the infections were found to be fertile, 18.90% sterile and 7.96% both sterile and partly calcified. Lung hydatids tended to be more fertile than liver cysts.