Onchocerca gutturosa and Onchocerca lienalis in cattle: effect of age, sex, and origin on prevalence of onchocerciasis in subtropical and temperate regions of Florida and Georgia

Evaluation of 845 cattle from Florida and Georgia for onchocerciasis indicated a significantly higher prevalence of infection with Onchocerca gutturosa and a significantly lower prevalence of infection with Onchocerca lienalis in the southern portion of Florida (subtropical region) than in the northern portion of Florida or in Georgia (temperature region). In all regions, prevalence of infection with O gutturosa was significantly higher than infection with O lienalis. In the temperate region, bulls were infected more often with O lienalis than were cows. Other sex-related differences in infection with either filariid was not found. Prevalence of infection with O lienalis was similar between age groups in all regions. Rates of infection with O gutturosa differed between age groups within and between subtropical and temperate regions. Examination of cervical and umbilical skin specimens for microfilariae detected an additional 6.6% of infected animals that had not been found by examination for adult worms. However, microfilariae were not found in 21.4% of animals that were positive for adult worms.     

Distribution of microfilariae of Onchocerca lienalis and Onchocerca gutturosa in the skin of cattle in Germany and their development in Simulium ornatum and Culicoides nubeculosus following artificial infestation

Onchocerca microfilariae were isolated form the umbilicus and neck of 438 cow hides at the abattoir in Tübingen, F.R.G. The overall Onchocerca infection rate was 40.4%. The presence of Onchocerca lienalis and O. gutturosa microfilariae, which are difficult to distinguish by morphological criteria, was retrospectively demonstrated after artifically infesting Simulium ornatum and Culicoides nubeculosus and identifying the infective larvae recovered. Nine of 16 samples of umbilical microfilariae fed to C. nubeculosus through a latex membrane developed to O. gutturosa third stage larvae (L3). Six of seven umbilical samples injected into the thorax of S. ornatum yielded O. lienalis L3. In six infestation trials in which microfilariae were introduced both into S. ornatum and C. nubeculosus, O. lienalis L3 were recovered exclusively from simuliids, while O. gutturosa L3 developed only in midges. Of six umbilical skins tested by cross-infestation, one contained exclusively O. gutturosa microfilariae, four only O. lienalis microfilariae and one was infected with both species. Developmental success of O. lienalis microfilariae to L3 in S. ornatum following intrathoracic injection was 22% of the mean inoculum. O. gutturosa microfilariae, ingested by C. nubeculosus through a latex membrane, developed to L3 at a rate of 2.3% of the mean microfilarial uptake.     

Distribution of Onchocerca spp. microfilariae in the dermis of cattle

A grid was drawn on a lateral half of 10 hides, from cattle infected with both Onchocerca gutturosa and Onchocerca lienalis, which were obtained from an abattoir in central Florida. Paired 7-mm diameter skin cores were taken from 24 grid sites on each hide and microfilariae (mff) extracted to determine their distribution. The only consistent pattern distribution was that mff were recovered from all 10 hides at four sample sites along the ventral midline near the umbilicus. Microfilariae were also frequently found in large numbers along the dorsal cervical midline and in the region of the tarsal and carpal-metacarpal joints.     

Ingestion of microfilariae from different sources by Culicoides nubeculosus (Diptera: Ceratopogonidae) through an artificial membrane

Laboratory-hatched Culicoides nubeculosus midges were membrane-fed on cattle blood containing various Onchocerca microfilariae which had been isolated from the hides of red deer (Cervus elaphus) and from Australian and native German cattle. All microfilariae were ingested through the membrane except those of O. tarsicola, which were too large. Onchocerca gibsoni and O. lienalis reached the thoracic musculature, but no further development occurred. Microfilariae of O. flexuosa developed to the "sausage" stage. Microfilariae of O. gutturosa developed to the infective larval stage within 9 days at a temperature of 25 degrees C.     

Teat onchocercosis in cows with reference to prevalence, species involved and pathology

The present study reports teat onchocercosis in cows in the province of Kars in north eastern Turkey with reference to the prevalence, species involved and pathological findings. In the study, 600 cows of various breeds and ages slaughtered in the local abattoir were examined and 145 (24%) were found to have various lesions on their teats, of which 45 (31%) were infected with three Onchocerca species (Onchocerca gutturosa, O. lienalis and an unidentified Onchocerca spp.), identified according to their morphological characteristics. Gross pathological examination of the teats with lesions revealed scabies and chaps of varying sizes, healed sores and small nodules. Histopathologically, large numbers of microfilariae were commonly observed within the collagenous fibre bundles of the dermis, with only a few microfilariae in the dermis in some cases. The microfilariae were also often found to have accumulated around the perivascular spaces and were frequently associated with infiltration by inflammatory cells, predominantly eosinophil leukocytes and mononuclear cells. In two cases, microfilariae were discovered exclusively in the lumen of the capillaries of the dermal papillaries. In one case, in which microfilarae were not encountered, sections of adult worms surrounded by neutrophil leukocytes were detected free in the teat canal. The presence of extensive teat lesions along with microfilariae of the Onchocerca species as found in this study warrants further assessment of the impact of onchocercosis on dairy farming.     

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.     

Ocular onchocercosis in dogs: aberrant infection in an accidental host or lupi onchocercosis?

Four adult dogs that had spent their entire life in Hungary, were found to be infected with filaroid nematodes of the genus Onchocerca. The morphology and location of the parasites as well as pathological lesions were similar to those described earlier in the one Hungarian and five US dogs. Only moderate morphological differences were noted between the adults of Onchocerca sp. infecting dogs and O. volvulus of man or O. lienalis of cattle. Nevertheless, the morphology of microfilariae of Onchocerca from dogs is unique within the genus. Their length was less than half the length of microfilariae of other Onchocerca spp. known so far. In addition to size differences, several characteristic morphological features were observed. The unsuccessful attempt to infect dogs with O. lienalis, the absence of O. volvulus and O. lienalis in endemic regions of canine onchocercosis, the different size, morphology, and location of the adults in dogs and cattle, the exceptionally small size and unique morphology of microfilariae of Onchocerca of canids indicate that a distinct species might be responsible for canine onchocercosis. Since the larval concentration in the skin was high (50-3600 microfilariae g(-1)) in all affected dogs, the diagnosis prior to surgical removal of worm nodules can be based on the examination of a small skin snip collected from the head or abdominal region. Infections in dogs may provide a model to study human onchocercosis, therefore, further studies are encouraged on the feasibility of experimental infection of dogs with this Onchocerca species.     

Onchocerca armillata Railliet and Henry, 1909 andOnchocerca gutturosa (Neumann, 1910) in camels (Camelus dromedarius L.) in the Sudan

A study undertaken to determine theOnchocerca species infecting camels that live in the same localities as cattle in the Dinder Region, Blue Nile Province, Sudan revealed concurrent infections with the bovine parasitesOnchocerca armillata in the thoracic aorta, brachiocephalic trunks and brachial arteries andOnchocerca gutturosa in the ventral side of the lamellar parts of theligamentum nuchae. The microfilariae of both species had the same predilection sites in the skin of the ears, head and neck regions. Those ofO. gutturosa outnumber those ofO. armillata but both are smaller than the respective uterine microfilariae. Males and microfilariae of both species are smaller than those of cattle origin.Part of the work was carried out while all the authors were at the Department of Parasitology, Faculty of Veterinary Science, University of Khartoum, Sudan.     

Simulium jenningsi Malloch (Diptera: Simuliidae): a vector of Onchocerca lienalis Stiles (Nematoda: Filarioidea) in New York

Biting flies were collected from the umbilical areas of Onchocerca lienalis-infected cattle in New York (state) from June through September of 1980. Of the 766 flies collected, 705 were Simulium jenningsi. Microfilariae were detected in the midguts of 37 (50%) of 73 females dissected immediately after the flies had fed. The mean number of larvae per positive fly (fly with microfilariae) was 15.2. Third-stage larvae were recovered from 25 (21.9%) of 114 S jenningsi dissected 8 to 13 days after they had fed on the infected cattle; the mean number of 3rd-stage larvae per positive fly was 3.5. Dissections of flies performed on days 1 through 7 after feeding yielded various numbers of 1st and 2nd-stage larvae from the thoracic muscles. Ovarian dissections performed on 304 S jenningsi attacking cattle indicated an overall parous rate of 58%. Naturally occurring infections with filarial larvae indistinguishable from O lienalis were found in 7.3% of the parous females. Three of these flies, or 1.7% of the parous collection, harbored 3rd-stage larvae. The onset of naturally occurring filarial infections in the population of S jenningsi coincided with a peak in the parous rate in late June. Thereafter, filarial infections were generally detected when the parous rate was above 50%.     

Onchocerca ochengi acquisition in zebu Gudali cattle exposed to natural transmission: parasite population dynamics and IgG antibody subclass responses to Ov10/Ov11 recombinant antigens

Ngaoundere Gudali zebu cattle naturally exposed to Simulium damnosum s.l. and Culicoides spp. bites were examined during 4 years for O. ochengi adult worm acquisition, Onchocerca ochengi and Onchocerca gutturosa skin microfilaria dynamics, and IgG1 and IgG2 antibody subclass responses. Eleven animals acquired a total of 465 O. ochengi nodules (average of 17 per female and 72 per male). The O. ochengi nodule load was highly variable in individual animals and exacerbated in mature male cattle. Three patterns of acquisition of O. ochengi (resistant to new infestation, early susceptibility and late susceptibility), not associated with Simulium biting intensity (P > 0.05), were distinguished. The minimum prepatent periods for O. ochengi nodules, O. ochengi microfilariae and O. gutturosa microfilariae were 10, 20 and 21 months, respectively. The O. ochengi microfilaria density significantly (P < 0.001) increased with age, was higher in young mature bulls than female animals (P < 0.001) and finally reached highest levels (P < 0.005) during the dry season. Antibody responses to Ov10/Ov11 recombinant O. volvulus antigens were predominantly of the IgG1 subclass. High levels of this subclass (not IgG2) observed in new born calves declined to almost zero levels at the age of 5-8 months but IgG1 levels significantly increased (P < 0.05) with age subsequently during patency. Put together the acquisition and accumulation of O. ochengi parasites in zebu cattle, apart from being season, sex (gender) and host age associated, may also suggest a density-dependent regulation of parasite establishment in a proportion of the exposed population.     

Prevalence of microfilariae in cattle at slaughter in Zaria, Nigeria

Skin snips and blood taken from 372 randomly selected slaughtered cattle in Zaria, Nigeria were examined for microfilariae. A total of 293 (78.8%) skin snips and 218 (58.6%) blood samples were positive for microfilariae. Two types of microfilariae, identified as Onchocerca armillata, with a percentage prevalence of 64%, and O. gutturosa with a prevalence of 40% were isolated from the skin. The blood microfilariae were identified as those of Setaria labiatopapillosa.     

Molecular genetic comparison of Onchocerca sp. infecting dogs in Europe with other spirurid nematodes including Onchocerca lienalis

In the past 15 years, subconjunctival onchocercosis has been reported from 63 dogs in south-western United States (Arizona, California, Utah) and Southern and Central Europe (Germany, Greece, Hungary, Portugal, Switzerland). To reveal the taxonomic status of the parasite responsible for these infections, fragments of the mitochondrial cytochrome oxidase subunit I (COI) and NADH dehydrogenase subunit 5 (ND5) genes of three European strains of canine Onchocerca sp. and the 16S ribosomal RNA (16S rRNA) gene of their Wolbachia endosymbionts were sequenced and compared to the homologous sequences of other spirurid nematodes. The evolutionary divergence between COI and ND5 gene sequences of Greek, Hungarian and Portuguese strains of canine Onchocerca sp. were similar in magnitude to that seen within Thelazia callipaeda or Onchocerca lienalis. The evolutionary divergence between the sequences of canine Onchocerca sp. and other Onchocerca spp. including O. lienalis were similar or higher in magnitude to that seen between other Onchocerca spp. The results of the current and earlier phylogenetic analyses indicate that canine Onchocerca sp. separated from other Onchocerca spp. early in the evolution. Based on the similar clinical pictures, the identical morphology of nematodes and the sequence analyses of COI and ND5 genes of the worms and 16S rRNA gene of their wolbachiae, the Onchocerca worms isolated from European dogs appear to belong to the same species. The results support the earlier biological and morphological arguments that a distinct species, most likely O. lupi originally described from the subconjunctival tissues of a Caucasian wolf is responsible for canine ocular onchocercosis in Europe.     

ONCHOCERCA GUTTUROSA IN Danish cattle. Prevalence, geographic distribution and host-vector relationships.

1. Onchocerca gutturosa is reported in Danish cattle for the first time. Microfilariae were found in 38 (9.4%) of 406 cows that were 2 years or older.
2. Microfilariae were not randomly distributed throughout the skin but were concentrated in the umbilical area.
3. No difference in prevalence was observed between breeds of cattle.
4. Most of the infected cows had grazed on fields close to streams that contained Simulium ornatum, the vector of O. gutturosa.
5. Differences in preferred biting sites of S. ornatum from cow to cow were correlated with the arrangement of hair.

     

Abomasal Nematodes in Cattle in Ontario

During 1970, 93 abomasa from cattle in Ontario were examined, and from 63 of these abomasa nematode species of the genera Ostertagia, Haemonchus and/or Trichostrongylus axei were recovered. The abomasa were from cattle six months to two years of age and were collected either from the postmortem room at the Ontario Veterinary College or from two abattoirs near Guelph. The numbers of worms per abomasum were estimated and their genera were identified from a one-twentieth volume of the washings and contents. The prevalence of Ostertagia species was estimated by examining random samples of adult male worms. Morphological variations in the species of the genera Ostertagia and Haemonchus were estimated by examining random samples of adult females. The predominant nematode was Ostertagia ostertagi. Other Ostertagia species recovered were O. trifurcata, O. lyrata and O. circumcincta. The numbers of nematodes recovered were generally low. Adult Ostertagia females had well-developed vulvar flaps. However, in abomasa where adult male O. trifurcata and O. lyrata were found, some adult female Ostertagia worms had reduced or no vulvar flaps. In two abomasa, adult Haemonchus females had large pendulous or “linguiform” vulvar flaps, and adult males had mean spicule lengths of 517 and 512 μ and were, therefore, unlike any of the recognized Haemonchus species.     

Characterization and purification of Parafilaria bovicola antigens by chromatofocusing to enhance specificity in serodiagnosis

A study was conducted to determine if the purification of Parafilaria bovicola antigens can increase the specificity of serodiagnosis of parafilariasis in enzyme-linked immunosorbent assay. Antigens released from adult worms of P. bovicola were separated by chromatofocusing on a polybuffer exchanger of the pH range 7.3-4.0 Polypeptide analysis by sodium dodecyl sulphate polyacrylamide gel electrophoresis showed the presence of four major polypeptides with MWs of 41, 36, 24 and 20 kDa. Additional biochemical characterization identified the 24- and 20-kDa polypeptides as hydrophobic glycoproteins. The chromatofocusing purification procedures were also applied for separation of a whole-worm extract. Again, the 41- and 36-kDa antigens were identified in separate peak fractions. Using ELISA, it was shown that the 41- and 35-kDa antigens were recognized by bovine antibodies specific for P. bovicola, but not by other sera collected from cattle infected by Onchocerca gutturosa, Onchocerca lienalis, Ostertagia ostertagi and Dictyocaulus viviparus. The serological evaluation strongly suggests that the 41- and 36-kDa antigens are P. bovicola specific.     

Blood flow and steroid and nutrient uptake of the gravid uterus and fetus of sows

Uterine and umbilical blood samples and blood flow (BF) measurements were obtained from one uterine horn and a single fetus of sows at d 70, 90 and 110 of gestation. Concentrations of O2 in blood and of estrogen (E), progesterone (P), glucose, alpha-amino nitrogen (N) and urea N in plasma were determined. Fetal weights were .267 +/- .018, .633 +/- .019 and 1.208 +/- .073 kg on d 70, 90 and 110, respectively. Uterine and umbilical BF remained constant with day of gestation, averaging 1.51 +/- .06 and .31 +/- .02 liters/min. Uptake of P by a uterine horn and fetus remained constant, but secretion of E by a uterine horn and uptake of E by a fetus increased (P less than .05) with stage of gestation. Uterine and fetal uptake of O2, glucose and alpha-amino N did not change and uptake of O2, glucose and alpha-amino N per kg fetus decreased (P less than .01) as gestation advanced. Secretion of urea N from the uterus was observed, with a concentration gradient from the fetal to the uterine circulations. Uterine and fetal respiratory quotients for glucose were .79 and .38, respectively. Thus, although glucose potentially served as a major energy source, a large portion of the energy requirements of the fetal pig were met by catabolism of other substrates. The decrease in umbilical BF and uptake of nutrients per kg fetus with day of gestation suggested that porcine fetal metabolism declined as pregnancy advanced.     

Efficacy of ivermectin against Onchocerca cervicalis microfilarial dermatitis in horses

Forty horses having microfilariae of Onchocerca cervicalis in association with dermatitis, alopecia, and pruritus on the ventral midline were given a single IM injection of 0.2 mg of ivermectin/kg of body weight (June to August 1981). Microfilarial counts in the 40 horses ranged from 18 to 42,446 microfilariae/skin snip on the day of treatment, and histopathologic examination of these skin sections indicated a chronic eosinophilic dermatitis. Numerous microfilariae were in the dermis, but there was no consistent relationship between the presence of microfilariae and the severity of the inflammatory reaction. In all 40 horses, skin snips taken 4 to 33 days after treatment were negative for microfilariae, and a marked clinical improvement occurred 2 to 3 weeks after treatment, when the lesion was replaced by healthy skin and new hair. Twenty-four hours after treatment, an edematous reaction occurred on the lower portion of the abdomen of 4 (10%) horses and within the area of the lesion in 6 (15% horses). The reactions disappeared within 24 to 72 hours, irrespective of whether horses were treated with corticosteroids. When further skin samples were taken from 15 horses 4 to 9 months later, 9 of them were free of microfilariae and the 6 others had only low counts (17 to 97). An additional 7 infected horses, treated when there was little chance of reinfection (November to December 1981), were all free of microfilariae at 6 to 10 days and 4 to 5 months after treatment. The marked clinical improvement in all horses after disappearance of microfilariae from the dermis indicates that microfilariae are involved in the cause and pathogenesis of the dermatitis.     

Onchocerca ochengi transmission dynamics and the correlation of O. ochengi microfilaria density in cattle with the transmission potential

The intensity of natural transmission of Onchocerca ochengi and Onchocerco volvulus by anthropo-boophilic Simulium damnosum s.l. was studied longitudinally in two cattle watering sites of a cattle ranch within a predominantly cattle populated area of the Guinea savanna of Cameroon and related to cattle O. ochengi skin microfilaria abundance. During the 12 months study period, a total of 4696 flies was individually dissected to examine the monthly transmission potential (MTP) of O. ochengi and O. volvulus. The estimated Simulium damnosum s.l. annual biting rates (ABR) on human baits were 47529 flies at the bank of the Vina "du sud" river. The ABR at the lake, which was situated at about 2 km upland from the perennial river, was 8579. The monthly parous rate was highly correlated with monthly biting rate. The annual transmission potentials (ATP) of O. ochengi were calculated to be 7732 and 1669 at the riverbank and the lake, respectively. Transmission occurred mainly in the dry season, peaking in the months of January to mid-March when dermal microfilaria density in the animals was also the highest. The O. ochengi microfilaria uptake by the fly vectors was host microfilaria density-dependent. The MTP of O. ochengi was positively correlated with dermal microfilaria density. The mean number of microfilariae per fly taken up during a blood meal was high during the dry season as was the mean number of infective larvae per fly but declined significantly with the onset of the early rains. A similar seasonality of transmission was also observed for O. volvulus that was concurrently transmitted by the same vector flies, but its ATP was comparatively much lower: 1332 infective larvae per man per year at the riverbank and 107 around the lake. The population dynamics of cattle microfilariae therefore plays an important role in the regulation of O. ochengi transmission.     

Onchocerca cervicalis in Horses from Southern Brazil

The objective of this study was to determine the occurrence of Onchocerca cervicalis in 1200 adult horses from rural areas of Rio Grande do Sul, Brazil. Umbilical skin specimens measuring 2 x 2 cm were minced, suspended in 10 ml of distilled water and incubated at room temperature overnight. The liquid volume was centrifuged and the sediment was screened for microfilariae. The ligamentum nuchae were totally removed, preserved in ice and dissected for the detection of adult forms of Onchocerca cervicalis. Microfilariae of Onchocerca cervicalis were detected in midventral skin biopsy samples in 215 (17.9%) of 1200 horses examined and the adult worms were recovered from 200 (16.6%) ligamentum nuchae from the same animals. These findings provide a basis for further studies to determine infection rates in horses from other regions of the state and to identify the intermediate host that transmits the disease.