Distribution of mast cells and their correlation with inflammatory cells around Onchocerca gutturosa, O. tarsicola, O. ochengi, and O. flexuosa.

In recent years, bovine Onchocerca species have been used as models for human onchocerciasis in drug screens. They have been suggested for immunology studies and evaluation of vaccine candidates. Therefore, mast cells and their association with other inflammatory cells were studied in five onchocercal species of cattle and deer using immunohistology. Intact mast cells occurred in large numbers in the capsule and septae of nodules, in fibrous tissue adjacent to nonnodular worms, and perivascularly. Inactive and, more frequency, activated and degranulating mast cells were observed within infiltrates in the nodule center or around nonnodular filariae. They were not detected in direct contact with the cuticle of adult worms or of microfilariae or among the macrophages, giant cells, and neutrophils forming the innermost layer around the worms. Eosinophils, but not mast cells, were obviously associated with microfilariae-producing females. The distribution, frequency, and activity of mast cells were similar for all five species and O. volvulus.

Onchocerca gutturosa infection of the ligamentum nuchae in two cows in the Sudan.

Severe lesions of the ligamentum nuchae are described for the first time in two cows in the Sudan. Post mortem and histopathological examination of the nodules reveals inflammatory process the causal agent of which is Onchocerca gutturosa.

Onchocerciasis in Minnesota cattle.

Umbilical hides from 536 dairy cattle in Minnesota were tested for the microfilarial stage of Onchocerca species to determine the distribution of onchocerciasis in the state. The infection was widespread as microfilariae were obtained from 214 (40%) of the animals, representing nearly all areas of the state. Adult Onchocerca parasites were collected primarily from nodules associated with tibial bones but also were found to a lesser extent within the gastrosplenic ligament. Specific identity of these organisms is unclear as they exhibit certain morphological features previously described as being characteristic of either Onchocerca gutturosa, Onchocerca lienalis, or Onchocerca stilesi.

Verification of ineffectual activity of ivermectin against adult Onchocerca spp in the ligamentum nuchae of horses.

Ivermectin paste formulation (200 micrograms/kg) was administered orally to 27 horses (13 Thoroughbreds and 14 of mixed breeding) to evaluate activity against adult Onchocerca spp in the ligamentum nuchae. Ages, known or estimated, of the horses ranged from 1 to 22 years. Single or multiple doses (1 to 5) of the drug were given to each horse. When multiple doses were administered, the intervals between treatments ranged from 7 to 92 days. At 27 to 171 days after initial treatment (single dose or first of multiple doses), the horses were killed. Some of the horses treated more than once were killed as soon as 7 days after the last treatment. At necropsy, Onchocerca spp were found in the ligamentum nuchae of 24 (89%) of the 27 horses. All of the specimens were pieces of worms, apparently adult, which appeared to be alive. The only noninfected horses were 2 to 3 years old. In 18 (75%) of the 24 infected horses, microfilariae, most being obviously viable, were found in the worm specimens or ligamentum nuchae.

Onchocerca spp: frequency in Thoroughbreds at necropsy in Kentucky.

Examination of the ligamentum nuchae for Onchocerca spp was completed in 523 Thoroughbreds (1 to 29 years old) at necropsy in Kentucky during a 13-month period (1984 to 1985). Onchocerca spp were found in 306 (59%) of the horses. Frequencies of this parasite were 3%, 17%, 40%, 43%, and 42% in 1-, 2-, 3-, 4-, and 5-year-old horses, respectively. For 6- to 29-year-old horses, frequency varied from 71% to 100%, except for 26-year-old horses (50%); 87% of the 304 horses examined in the 6- to 29-year-old age groups was infected. The suspensory ligaments and flexor tendons from fetlocks (thoracic limb only) of 100 Thoroughbreds (3 to 24 years old) were examined at necropsy during a 4-month period (1984) for Onchocerca spp. Infected horses were not found.

[Occurrence of Onchocerca lienalis (Stiles, 1892) in cattle in Austria]. / Uber das Vorkommen von Onchocerca lienalis (Stiles, 1892) bei Rindern in Osterreich.

The prevalence of O. lienalis in 345 Austrian cattle was determined by detection of microfilariae in the skin. Though only one among 59 male animals yielded a positive result, 46.5% of the female cattle showed to be infected with the parasite. Comparing the presence of adult worms in the gastrosplenic ligament and that of larval stages in the skin a correlation of 87.5% could be obtained. Most of the microfilariae were concentrated in the umbilical region but with severely infested animals they also were found in the skin of the udder, head, ear and neck. Seasonal periodicity of microfilariae was not observed.

Morphological characteristics and isoenzyme patterns of an Onchocerca sp. found in cattle in Southern Mexico.

An Onchocerca sp. was isolated from the nuchal ligaments of 78 out of 79 naturally infected cattle in Southern Mexico. Infections were moderate to heavy, averaging 20-30 parasites per nuchal ligament. Microfilariae were concentrated in the skin of the head and neck, although small numbers were found in the skin of the withers, brisket and medial abdomen. High numbers of microfilariae were found in the skin around the eye, but not in the ocular tissues themselves a situation dissimilar to that found in human onchocerciasis. Morphologically, adult females, males and microfilariae were identified as being O. gutturosa. Analysis of the isoenzyme patterns of LDH, MDH, PGM, GPI, PGD and ES of adult female worms, showed the Mexican parasite to be the same as O. gutturosa from England and Australia.

Equine onchocerciasis: lesions in the nuchal ligament of midwestern U.S. horses.

Nuchal ligaments from midwestern U.S. horses infected with adult Onchocerca sp. were studied. The prevalence of Onchocerca sp. infection in horses increased with age. Ten percent of horses less than one year old were infected, 28% of horses one to five years old, 48% of horses six to 15 years old, and 90% of horses over 16 years old. Lesions in Onchocerca sp.-infected nuchal ligaments varied with age of the horse. Horses less than five years old had few or no lesions, whereas most horses six to 15 years old had focal mineralization and granuloma formation around adult worms. In infected nuchal ligaments of horses over 16 years old, mineralization was much greater and fewer normal parasites were found. Our data suggest that infection by viable parasites is terminated naturally.

Bovine and equine onchocerciasis in eastern North America with a discussion on cuticular morphology of Onchocerca spp. in cattle.

Skin sections and/or the ligamentum nuchae and ligamentum gastrolienale were examined from twelve bovine carcasses obtained from southern and eastern Ontario and from Quebec. Of these, seven were shown to be infected with Onchocerca gutturosa and/or Onchocerca lienalis. The morphology of the adult female cuticle is discussed. Skin sections from 43 equine carcasses from a slaughter house in Grenville, Quebec were examined and microfilariae of Onchocerca sp. were recovered from 32 (74%). There are probably referable to Onchocerca cervicalis.

[Validity of the two species O. lienalis and O. gutturosa from bovines (author's transl)]. / Validité des deux espèces Onchocerca lienalis et O. gutturosa, chez les bovins.

A new morphological analysis of the Onchocerca from the gastrosplenic ligament reveals characteristics confirming the validity of the species O. lienalis as distinct from the cervical Onchocerca, O. gutturosa. The dermic microfilaire of the two species have completely different distributions: the microfilariae of O. gutturosa are gathered in the cephalic region of Bovines while that of O. lienalis can be found in the umbilical region. Therefore we suspect strongly that the life cycle evolving in S. ornatum in England is that of O. lienalis and not of O. gutturosa as previously postulated; and we think that O. gutturosa is more likely to evolve in Culicoides than in Simulium.

Bovine onchocerciasis caused by Onchocerca armillata and O. gutturosa.

Onchocerca armillata was found in 284 (28%) of 1,016 aortas, and O. gutturosa in 82 (28.87%) of 284 nuchal ligaments and in 11 (7.85%) of 140 rumenosplenic areas in specimens from cattle slaughtered during a 12-month period. Adult parasites were not found in 600 hides. Gross lesions included parasitic tunnels, nodules, roughening and calcification in the aortic walls. The connective tissue of nuchal ligaments and rumenosplenic areas was increased in amount, was gelatinous and brown and had afew nodules, Microscopically there were acute changes with oedema, haemorrhages and cellular infiltrations predominatly by eosinophils. There were chronic granulomatous reactions characterized by accumulation of macrophages, lymphocytes, plasma cells, giant cells, calcification and fibrosis around degenerate and dead parasites. Neutral fat was in parasites and surrounding cells. Both changes often occurred in the same specimen and many samples had parasites but no tissue reaction. Hypersensitivity, foreign-body reactions and parasitic toxins apparently were involved in the genesis of these lesions.