Colonisation and degradation of dung pats after subcutaneous treatment of cattle with ivermectin or levamisole

The fauna and degradation of dung pats from cattle treated with ivermectin or levamisole were examined in a field study conducted in southern Germany. Four groups of seven cattle each grazed on four paddocks. The cattle were treated subcutaneously with ivermectin (0.2 mg/kg) or levamisole (5 mg/kg) 3, 8 and 13 weeks after turnout. A total of 300 pats voided naturally before the first and third treatment and 3, 7, 14 and 28 days after treatment were evaluated. Half of them were used as sampling pats, in which adult and immature Coleoptera, larvae of Diptera and soil and dung nematodes were counted. Earthworms were weighed in samples taken on 8 occasions within 63 days after pat deposition. Dung degradation was investigated using 150 observation pats by measuring surface area, weight and organic matter content on six occasions within 63 days from deposition. A photographic record was also maintained. There was no difference between treatment groups as to the range of Coleoptera, nematodes and earthworms collected from the pats. No quantitative differences between groups were seen regarding the total number of adult and immature dung beetles, soil nematodes and earthworms isolated within 63 days after deposition. Populations of Diptera larvae in pats voided up to 28 days after treatment were reduced for the ivermectin treated group relative to the levamisole group. There were reductions in numbers of dung specific nematodes in pats from both groups and some species were reduced in pats deposited 3, 7, and to a lesser extent, 14 days after treatment for the ivermectin group compared with pats from the levamisole group. These effects on dung fauna had no impact on dung degradation. The results of serial measurement of pat area, photographic evaluation, and determination of remaining dung weight and organic matter showed no difference between treatment group.

Isolation and characteristics of the protozoal and bacterial fractions from bovine ruminal contents

Four cows were fed once a day either a Cocksfoot hay diet (H) or a diet consisting of 65% hay and 35% pelleted ground barley (HB). 15(NH4)2SO4 was continuously infused into the rumen as a microbial marker and ruminal digesta samples were collected during the 24-h postprandial period for the isolation of liquid-associated protozoa and bacteria (LAP, LAB) and particle-associated bacteria (PAB). There were marked differences between ruminal pH diurnal variations with diets H and HB. Irrespective of the diet and sampling time, the chemical composition (OM, N, DAPA, 15N) of the protozoa was clearly different from that of the bacteria (P < .001). The LAP contained more OM but less N and 15N than the bacterial fractions. The DAPA used to validate the isolation technique for the mixed ciliate population was not detected in protozoal fractions. The OM content of LAB was lower than that of PAB, whereas the N, DAPA, and 15N contents were higher. The observed effects of diet (P < .01) on LAP mean N contents were due to the different N contents of the LAP samples isolated 23 h after feeding and were correlated with the variation in the number of Endodiniomorphid protozoa (r = .72; P < .05). The N content of LAB was not affected (P > .05) by diet but that of the PAB was increased on diet HB (P < .05). The diet did not affect the 15N content of any of the three microbial populations. However, the 15N content of the bacteria decreased shortly after feeding (P < .001).

Effects of housing and colostrum feeding on the prevalence of selected infectious organisms in feces of Jersey calves

Neonatal Jersey calves (n = 96) were used to evaluate effects of housing (individual hutches or wooden pens in a barn) and colostrum feeding (calves were separated from the dam and fed 2 L of colostrum in nipple-bottles or allowed to nurse the dam for 3 d) on the prevalence of selected organisms in feces. Prevalence of Cryptosporidium and Eimeria were reduced, and prevalence of rotavirus tended to be reduced, when calves were housed in hutches. Prevalence of coronavirus was unaffected by treatment. Weekly prevalence of Giardia was increased when calves were left to nurse the dam for 3 d. Mean prevalence of Cryptosporidia (wk 1 to 4), Eimeria (wk 4 to 5), Giardia, rotavirus, and coronavirus (wk 1 to 5) were 34.7, 20.6, 27.1, 15.8, and 4.9%, respectively. Escherichia coli (K99 positive) were observed in 3 of 174 samples cultured. Methods of housing and colostrum feeding affected acquisition of enteropathogens in this study.

The effects of Onchocerca lienalis infection on vitellogenesis in the British blackfly, Simulium ornatum

We have previously described the major yolk protein, vitellin, in the British blackfly Simulium ornatum Meigen. Here we demonstrate that vitellogenin, synthesized in the fat body and secreted into the haemolymph, is composed of subunits with the same approximate molecular weight as vitellin, namely 200 and 68 kDa. Simulium ornatum is the natural vector for the cattle filarial nematode Onchocerca lienalis Stiles, which induces host fecundity depletion. A significant reduction in ovarian vitellin content was associated with infection by intrathoracic injection of 20 O. lienalis microfilariae immediately after blood-feeding. Fat body synthesis of vitellogenin was significantly reduced as early as 8 h post-infection in comparison with sham-injected flies. When total haemolymph protein from infected and sham injected flies was compared, titres were significantly depressed 6 h post-infection. However, later in the infection, titres were elevated by 30%, the major component being vitellogenin. The injection of dead microfilariae had no effect. An infection burden of a single parasite caused a significant reduction in ovarian protein content in comparison with shams, but no further significant decrease was observed as the parasite burden was increased from 5 to 20. Possible mechanisms underlying the disturbance of Simulium reproductive physiology are proposed.

Host feeding patterns of Culex vishnui sub group of mosquitoes in Dibrugarh district of Assam

The host feeding patterns of three species of mosquitoes belonging to vishnui sub group, Culex tritaeniorhynchus, Culex vishnui and Culex pseudovishnui, the most prevalent species in Dibrugarh district were determined by analysing their blood meals. All 3 species were found be essentially zoophilic. High percentage of pig feeding was observed in Culex tritaeniorhynchus (40 per cent) and Culex vishnui (35.3 per cent) in comparison to other prevalent species in this area. In contrast Culex pseudovishnui another member of this group was not attracted to pigs (0.4 per cent). Few human feeds were recorded for Culex tritaeniorhynchus (0.4 per cent), Culex vishnui (0.4 per cent) and Culex pseudovishnui (0.8 per cent), indicating their occasional contact with human hosts. Considering the importance of this group as proven vectors of Japanese encephalitis the relevance of these results to JE transmission in this area are discussed.

Genetic variation in the triploids of Japanese Fasciola species, and relationships with other species in the genus

Twelve enzymes (encoded by 14 loci) in liver flukes of Fasciola species originating from Japan (parthenogenetic triploids), Korea (parthenogenetic diploids), the United States of America (USA) and Australia (all sexual diploids) were analysed using starch gel electrophoresis. Variation in electrophoretic patterns between samples was detected at fic enzyme loci (Ak, Got, Gpi, 6-Pgd and Pgm-2). Japanese worms (31, of which six were established as uniparental laboratory strains), which reproduce by parthenogenesis, exhibited three different isozyme patterns. This indicates that triploidy has arisen more than once in Japanese flukes. Japanese Fasciola sp. can be separated into three types on morphological grounds. For the six laboratory strains of Japanese worms, the parental morphological type was known. Each of the three isozyme patterns observed was restricted to one morphological type. Most alleles detected in the Japanese triploids were also found in diploid worms from the other countries: the only alleles not represented elsewhere were four at the Got locus and two at the Pgm locus. Flukes from a laboratory strain derived from a single Korean diploid worm resembled the Japanese worms in genotype more closely than did America (seven uniparental laboratory strains) or Australian (30 worms) specimens. Worms from the last two countries were closely related.

Rumen ciliate composition and diversity of Japanese beef black cattle in comparison with those of Holstein-Friesian cattle

The composition of ciliate protozoa in the rumen of 30 Japanese beef black cattle (Bos taurus taurus) fed in Yoron Island, Kagoshima, was compared with that of 125 Holstein-Friesian cattle (Bos taurus taurus) fed in Hokkaido. Thirteen genera including 44 species with 32 formae detected from Japanese beef black cattle and 15 genera including 48 species with 25 formae from Holstein-Friesian cattle were identified. Thirty-six species with 19 formae were common to both hosts. A new species was recognized from Japanese beef black cattle and named Entodinium yunnense n. sp. This new species was classified into such four formae as yunnense n.f., spinonucleatum n.f., acutonucleatum n.f. and spinolobum n.f. A new forma of Entodinium bifidum having only one caudal spine was also recognized from Japanese beef black cattle and named monospinosum n.f. The average ciliate density in Japanese beef black cattle, 18.7 x 10(4)/ml, was lower than 40.3 x 10(4)/ml in Holstein-Friesian cattle. The average number of ciliate species per head in Japanese beef black cattle, 14.4 was also lower than 17.8 in Holstein-Friesian cattle. The average value of diversity index was 1.789 in Japanese beef black cattle and 1.718 in Holstein-Friesian cattle. Both incidence and composition ratio of Entodinium rectangulatum and E. ovinum were significantly higher in Japanese beef black cattle than in Holstein-Friesian cattle. On the other hand, Charonina ventriculi, E. caudatum, E. rostratum, E. parvum, E. bursa, Metadinium affine and Ostracodinium mammosum showed a reverse relation.

A comparison of sampling methods with respect to cattle-visiting Muscidae and their nematode infections

Cattle-visiting Muscidae were sampled with a handnet from a blood-smeared Masonite panel as well as grazing heifers and dairy cows in south-central Sweden. All flies were examined in search of nematodes. Only Musca autumnalis was infected with nematodes (Parafilaria bovicola, Thelazia spp. and Heterotylenchus autumnalis). The only mixed infections found involved P. bovicola and Thelazia spp. Most M. autumnalis infected with P. bovicola and Thelazia spp. were found during the two first months of the grazing season, whereas the prevalence of specimens infected with H. autumnalis remained about the same throughout the sampling period. Musca autumnalis was caught in significantly smaller numbers from heifers (P < 0.05) than from panel and cows. The catches of nematode-infected M. autumnalis were similarly distributed. Catches of other cattle-visiting Muscidae did not differ significantly among the methods used. Handnet sampling off a panel is therefore considered to be a convenient and accurate method when investigating the abundance of cattle-visiting Muscidae and the prevalence of their nematode infections.

The effect of long-term exposure to anthio on serum esterases and ruminal microorganisms of male calves

The effect of long-term exposure to the organophosphate insecticide Anthio on serum esterases and ruminal microorganisms of male calves was investigated. The daily oral administration of 3, 6 or 12 mg Anthio/kg/d for 90 d caused significant inhibition of serum cholinesterase (10-28%) and carboxylesterase (12-33%) in male calves. Toxic signs characteristic of anticholinesterase poisoning were observed during 25-70 d of exposure to 6 and 12 mg Anthio/kg. The dose of 12 mg Anthio/kg was lethal to 1/5 calves. Total protozoal population was decreased significantly (15-27%) following 6 and 12 mg Anthio/kg, whereas reduction in total bacterial population (18%) was only significant at 12 mg Anthio/kg.

Comparative genetic analysis of Swiss and Spanish isolates of Echinococcus granulosus by southern hybridization and Random Amplified Polymorphic DNA technique

Swiss and Spanish isolates of Echinococcus granulosus were compared using different molecular biological techniques: Genomic DNAs isolated from parasites originating from various intermediate hosts were subjected to Southern hybridization with different probes, the same source of DNA was used for DNA amplification using the Random Amplified Polymorphic DNA (RAPD) technique. With both methods the various isolates (metacestodes) of E. granulosus exhibited characteristic banding patterns which allowed us to assign them to the following groups of homologous profiles: (a) isolates of horse and donkey origin from Spain and Switzerland; (b) isolates of cattle origin from Switzerland; (c) isolates of sheep, cattle and human origin from Spain; (d) isolates of pig origin from Spain and Switzerland and of goat origin from Spain. By RAPD (Southern hybridization not examined) two isolates of human origin from Switzerland were showing banding patterns distinct from groups (a-d). The results provide further evidence that the morphological and biological differences of several strains of E. granulosus are also detectable on the genetic level using molecular biological techniques.

Seroepidemiology of Toxoplasma gondii (Apicomplexa) in meat producing animals in Costa Rica

A serologic screening for Toxoplasma gondii antibodies by IgG indirect fluorescent antibodies test (IgG-IFAT) was carried among 496 swine and 601 cattle serum samples from throughout Costa Rica, to study the possible role of their meat in the transmission of the parasite. The overall prevalence of antibodies was 34.4% in cattle and 43.8% in swine. No significant differences were found in the antibody prevalence between males and females in both animal groups, which acquire the infection early in their lives. Swine did not present significant differences between age groups. In cattle there was a high percent of seropositivity between the first and third years of age. The provinces that showed a greater number of seropositive animals were Limón and Puntarenas for both animals, and Guanacaste for cattle.

Examination of possible transmission of sheep scab mite Psoroptes ovis between host species

Examination of possible transmission of the Irish strain of the sheep scab mite (Psoroptes ovis) of ovine origin between host species involved calves and goats being placed with infected sheep and also directly challenged with live mites. Although mites remained on recipient species for up to a week, they failed to produce disease in either of these species. Calves and goats that had live mites placed on them likewise failed to infect sheep with which they were housed.

Efficacy of Brahman breeding in the management of insecticide-resistant horn flies (Diptera: Muscidae) on beef cattle

The efficacy of Brahman breeding used as an alternative tactic to manage insecticide-resistant populations of adult horn flies, Haematobia irritans irritans (L.), was determined. Concentration-mortality bioassays done at Booneville and Hope, AR, in 1988 and 1989, respectively, showed that horn fly populations were resistant to diazinon, pirimiphos methyl, tetrachlorvinphos, and methoxychlor. Data showed loss of field efficacy for coumaphos and delnav. Mean horn fly counts on Braham cows were significantly lower than on Angus cows for all sampling dates in 1989 and 1990. Mean fly counts on Brahman x Angus cows were approximately intermediate to the two purebred mean fly counts. Brahman breeding caused significant reductions in the number of organophosphate-resistant horn flies, which had been equal to or greater than that obtained from continued spraying with organophosphate insecticides. The Brahman x Hereford cows, which have one-eighth greater Brahman breeding than the Brangus cows, had fewer horn flies on 48 of 56 sampling dates in 1988-1990 and significantly fewer flies on 37 sampling dates. The effectiveness of Brahman breeding in causing lower numbers of insecticide-resistant horn flies significantly increased as the percentage of Brahman breeding increased.

Development and distribution of bovine trichostrongyle infective larvae on a pasture irrigated by flooding or by spraying

To compare the ecological effects of irrigation of a pasture, by flooding or by spraying, on the gastro-intestinal parasites of calves, two contiguous plots, one flooded and the other sprayed, were grazed for 10 days by naturally infected animals. Faeces, grass and soil under pats were sampled for 17-20 weeks for larval counts. The experiment was performed once in the spring and once in the summer. In the spring the maximal development rates in sprayed and flooded plots were 7.8 and 12.6 stage 3 larvae (L3)/100 eggs, respectively, for Cooperia and 3.5 and 3.2 L3/100 eggs, respectively for Ostertagia. During the summer, development rates were less than 1%. The main differences were found in the vertical distribution of the larvae: spraying favoured migration on grass and flooding favoured migration in soil, this finding being similar for both genera. The spatial distribution, studied by dividing each plot into 18 subplots, was a little more regular on grass in the sprayed plot. We conclude that the infection risk for calves is lower in flooded pasture than in sprayed pasture.

Identification of bloodmeals of the Scottish biting midge, Culicoides impunctatus, by indirect enzyme-linked immunosorbent assay (ELISA)

An indirect enzyme-linked immunosorbent assay (ELISA) has been developed to identify the bloodmeal sources of Culicoides impunctatus Goetghebuer. Nightly light trapping in Scotland, between April and September 1992, caught a total of 344 blood-engorged female C. impunctatus, all in May, June and July. The insects were stored in 70% ethanol and tested 5-7 months later. Bloodmeal sources were positively identified for 246 (71.5%). Bovine hosts were most common (38.4%), followed by deer (23.0%) and sheep (9.9%). Only one midge had fed on human blood. Relatively freshly fed (< 24 h), fully engorged females gave the clearest results. The wider applications of the technique to the study of Culicoides host preferences is discussed.

Cattle-tsetse contact in relation to the daily activity patterns of Glossina morsitans submorsitans in The Gambia

The daily flight activity patterns of one of the main vectors of animal trypanosomiasis in West Africa, Glossina morsitans submorsitans, were assessed using four different methods. Results from all the methods showed that there was some flight activity nearly every hour in all seasons but they differed in the level of contact between grazing cattle herds and G.m.submorsitans. In the late dry season, trap data indicated that there was negligible activity from midday to late afternoon, whereas observations of tsetse contact with cattle herds or hand-net collections on herd followings showed no fall in attack rates, on the cattle by G.m.submorsitans. Differences between trap and animal-baited collection data may be attributable to the type of G.m.submorsitans sampled by each method. Male G.m.submorsitans captured by traps were more fat depleted than those caught on ox-baited flyrounds or by hand-net collections on herd followings. All methods showed that male G.m.submorsitans were most fat depleted in the late dry season and least in the early dry season. It was concluded that the traps were mainly sampling the spontaneous flights of G.m.submorsitans. Hunger and endogenous rhythms increase the likelihood of spontaneous flights towards dusk, particularly in conditions such as those at midday in the very hot, late dry season. However, the presence of cattle herds in infested habitats probably activated nearby G.m.submorsitans and the continual movement through the grazing areas ensured contact with tsetse throughout grazing.(ABSTRACT TRUNCATED AT 250 WORDS)

Culicoides aspirated from cattle in Costa Rica, Honduras, Panama and Puerto Rico, and their role as potential vectors of bluetongue viruses. Regional Bluetongue Team

In 1991, as part of an epidemiological study of bluetongue viruses (BTV) in the Central American and Caribbean region, eight farms located in Costa Rica, Honduras, Panamá and Puerto Rico were sampled for Culicoides spp. attacking cattle. Using cattle bait, 3884 biting midges were collected with an electric aspirator during both crepuscular periods. The predominant species captured was Culicoides insignis Lutz (95%), followed by C.furens (Poey) (3.4%), C.filarifer Hoffman/C.ocumarensis Ortiz (0.9%), C.lahillei (Iches) (0.7%), C.arubae Fox and Hoffman (< 0.1%) and C.gorgasi Wirth and Blanton (< 0.1%). Blood-engorged specimens from some of these species were collected and comprised: 18% of all C.insignis, 36% of C.furens, 37% of filarifer/ocumarensis and 25% of C.lahillei. No engorged C.arubae or C.gorgasi were caught. These results confirm earlier findings pointing to C.insignis, C.furens and C.filarifer/ocumarensis as potential vectors of BTV in the region.

The effect of multiple transfers of immune serum on maturing Schistosoma bovis infections in calves

To investigate the role of humoral factors in immunity, serum from cattle with naturally acquired immunity to Schistosoma bovis was injected intraperitoneally into calves that had been infected 4 weeks earlier with 10,000 S. bovis cercariae. Serum was injected weekly until 12 weeks post-infection to a total of 4,500 ml per calf and controls received normal serum or saline. No significant difference in worm or in faecal or tissue egg counts were seen in the three groups of recipients in spite of the observation that the serum donors had proved highly resistant to experimental challenge. In a second experiment, pre-infection or 4-, 8- or 12-week post-infection serum from donors given a single experimental infection with 10,000 S. bovis cercariae was injected intraperitoneally into groups of calves that had been infected 4 weeks earlier with 20,000 S. bovis cercariae. Injections were given weekly up to week 10 post-infection to a total of 2000-3500 ml serum per calf. In calves injected with immune serum there was a reduction in faecal and tissue egg counts and in the numbers of worms recovered as compared with the controls. In recipients of 8- and 12-week serum the reductions in faecal and tissue egg counts were higher than those in worm recovery, suggesting that 8- and 12-week post-infection sera contained factors capable of causing, in addition to worm death, suppression of worm fecundity. This provides further evidence of the importance of fecundity suppression in immunity to schistosomiasis.

Oligonucleotide probes complementary to variable regions of 18S rRNA from Sarcocystis species

Sarcocystis is a large genus of cyst-forming coccidian parasites in the phylum Apicomplexa (Protista). Stable RNA was extracted from cystozoites of Sarcocystis cruzi, S. tenella, S. fusiformis, S. gigantea and Toxoplasma gondii. The partial sequences of the small sub-unit ribosomal RNA (18S rRNA) were determined by direct RNA sequencing with reverse transcriptase. The rRNA sequences were computer aligned with the published partial sequence of T. gondii, and three oligonucleotides complementary to different variable regions of the 18S rRNA were synthesized. The three probes were end-labelled with 32P and tested in filter hybridization experiments. One of the probes designed to be Sarcocystis genus-specific, did not cross-hybridize to stable RNA from T. gondii. Two of the probes were designed to be species-specific for S. cruzi and S. tenella, and these probes hybridized specifically with their respective targets.

Development of Trypanosoma (M.) theileri in tabanids

Thus far the life cycle of Trypanosoma (Megatrypanum) theileri has not been studied. We collected tabanids during the mass hatching, when only few tabanids are infected with trypanosomes. Tabanids were caught immediately after attacking a bait cow to serve as controls or after they had been allowed to engorge on the Trypanosoma (M.) theileri-infected cow. Tabanids were kept in the laboratory and used to study the developmental cycle of T. (M.) theileri in the tabanid gut. From day 1 to day 10 the presumably unfed controls and the engorged tabanids were dissected and cytological smears made from the mid- and hindgut. In total 2.6% (1/38) of the controls and 39% (23/59) of the engorged tabanids were positive for trypanosomes in the 1991 season. From day 1 to day 4 after engorgement trypanosomes were found in the midgut. Epimastigotes with a length of 29 microm on day 1 after infection multiplied by inequal division to form smaller epimastigotes of 26 microm on day 3. On day 4 morphologically indistinguishable trypanosomes of 21 microm total length were found in both mid- and hindgut. From day 5 to day 10 trypanosomes were found only in the hindgut in which the transformation to metacyclics was demonstrated, i.e., epimastigotes transformed to amastigote stages of 5 microm in total length.

Stagewise mortality, ovipositional biology, and egg viability of Boophilus annulatus (Acari: Ixodidae) on Boselaphus tragocamelus (Artiodactyla: Bovidae)

The stagewise mortality, ovipositional biology, and egg viability of the cattle tick, Boophilus annulatus (Say), on nilgai antelope, Boselaphus tragocamelus Pallas, was compared with ticks reared on Bos taurus (Hereford) cattle. Mortality was highest during the larval stage on both host species, but larval mortality on nilgai (78.6%) was significantly higher than on cattle (45.6%) hosts. Mortality during the nymphal stage was also significantly higher on nilgai (49.3%) than on cattle (13.9%). During adult female development, although the mortality rate on nilgai was 40.9% compared with no mortality of females on cattle, this difference was not significant. Significantly fewer ticks reached repletion on nilgai (4.0 females per animal) than on cattle (48.5 females per animal). The mean female weight and egg mass weight of ticks obtained from cattle were significantly higher than ticks produced from nilgai. On the other hand, no differences in mean conversion efficiency index (CEI), preoviposition period, incubation period, or egg hatch were observed among ticks obtained from the two host animals. Although nilgai produce fewer replete females, and the females that do survive are smaller and produce smaller egg masses, nilgai cannot be disregarded in an eradication program. The fact that even a small number of viable ticks is able to reproduce successfully on nilgai could lead to the failure of current eradication strategies by compromising the required quarantine interval.

The nutritional state of male tsetse flies, Glossina pallidipes, at the time of feeding

The feeding intervals of tsetse flies have been estimated from the nutritional state of flies caught in traps. However, such estimates have been disputed on the grounds that traps catch a biased, hungry sample of the flies which are seeking hosts and will feed. In this paper we present data on the nutritional state of tsetse flies caught approaching and feeding on oxen. Individual oxen were surrounded with an incomplete ring of electric nets which caught Glossina pallidipes Austen that were approaching, departing unfed and departing fed from an ox. Non-teneral males caught in this way were analysed for their fat and haematin contents. The feeding interval was estimated from a comparison of the frequency distributions of the pre- and post-feed haematin contents of the flies which fed. The former was not measured directly, and was deduced from the frequency distributions of the haematin contents of the male flies caught approaching and departing unfed from the oxen, since it is assumed that the departing unfed and fed flies together form a sample of the approaching flies. There was no difference between the frequency distributions of haematin contents of flies caught approaching and departing unfed, and therefore the pre-feed haematin contents of the males which fed should have the same frequency distribution. Comparison of this distribution with that of the post-feed haematin contents of the males which fed indicated that the majority of male G.pallidipes were returning to feed after digesting on average 1.4 log haematin units of the previous bloodmeal.(ABSTRACT TRUNCATED AT 250 WORDS)

[Epidemiologic study of Lyme disease in Asturias]

BACKGROUND

The aim of this study was to confirm the Sierra del Sueve (Asturias) as an endemic area for Lyme's disease and determine the seroprevalence of this disease in inhabitants of this and other zones of Asturias.

METHODS

A taxonomic study of 233 ticks in this county was carried out and the rate of infection by Borrelia burgdorferi was determined by culture in modified Kelly medium. Seroprevalence of Lyme's disease was studied by enzyme-immunoanalysis IgG-IgM in 150 inhabitants from several counties of Asturias.

RESULTS

The tick Ixodes ricinus is the most abundant species in the zone. All the cultures of Ixodes for Borrelia burgdorferi were negative. Among the farmers of the area of Sueve, seroprevalence of Lyme's disease was higher than in other population groups.

CONCLUSIONS

The Sierra del Sueve is an endemic area of Lyme's disease because of the appropriate vector I. ricinus and the super-population of Fallow deer. In this county the percentage of asymptomatic seropositives for this disease is much higher than that of other zones in Spain.

New version of LSTSIM for computer simulation of Amblyomma americanum (Acari: Ixodidae) population dynamics

A previous version of Lone Star Tick Simulation Model (LSTSIM) for a wildlife ecosystem was revised and expanded to include a beef cattle forage area and improved handling of tick-host-habitat interactions. Relationships between environmental and biological variables were also refined in the new version. General validity of the revised model was established by comparing simulated and observed host-seeking populations of Amblyomma americanum (L.) at five geographic locations, three in Oklahoma and two in Kentucky-Tennessee. Additional validity was indicated from comparisons of simulated and observed seasonality of lone star ticks at one location in Kentucky. The model produced acceptable values for initial population growth rate, generation time, and 15-yr population density when historical weather files for 14 locations in the United States were used. The model of A. americanum population dynamics was used to study the relationship between tick density and density of white-tailed deer, Odocoileus virginianus (Zimmerman), and cattle. The revised model can be used for additional simulation studies on effects of tick control technologies and integrated management strategies.