C. D. Steelman

Detection of Campylobacter and Escherichia coli O157:H7 from filth flies by polymerase chain reaction.

Abstract.  Flies (Diptera: Muscidae) that breed in faeces and other organic refuse (filth flies) have been implicated as vectors of pathogenic bacteria including Escherichia coli O157:H7, which cause haemorrhagic colitis in humans, and Campylobacter, which is the principal causative agent of human enteritis. The potential role of filth flies in the epidemiology of these pathogens in the United States was investigated by examining the prevalence of Campylobacter spp. and E. coli O157:H7 from two Arkansas turkey facilities. Polymerase chain reaction was conducted on DNA extractions of individual Musca domestica Linnaeus, Stomoxys calcitrans (Linnaeus), Hydrotaea aenescens (Wiedemann), Adia cinerella Fallen and turkey faecal samples using primers specific for E. coli H7, O157 and Campylobacter spp. Culturing verified that the flies were carrying viable Campylobacter spp. and E. coli O157:H7. Results from this study indicated that M. domestica, S. calcitrans, H. aenescens and Anthomyids are capable of carrying Campylobacter in North American poultry facilities and that the E. coli O157:H7 is carried by house flies and black dump flies associated with poultry. This PCR method provided a rapid and effective method to identify Campylobacter spp. and E. coli O157:H7 directly from individual filth flies.

The effects of hair density of beef cattle on Haematobia irritans horn fly populations

Abstract We show the relationships that exist between the amount of hair and quantity of sebum on cattle skin and the population density of the horn fly, Haematobia irritans. Brahman and Chianina steers had means of 2390 and 1587 hairs per cm2, respectively, significantly more than the mean number of hairs on Angus, Brahman x Angus Crossbred, Charolais, and Red Poll steers. The Chianina steers had > 30% more sebum present on their skin and hair (0.58g/929cm2) than the Angus, Charolais, and Red Poll steers at the Beef Cattle Research Station Savoy, Arkansas. The Brahman steers had a significantly greater amount of sebum present on the skin (1.51 g/ 929 cm2) than the Crossbred and purebred Angus steers (0.55 and 0.25g/929cm2, respectively) at the South Central Family Farms Research Centre Booneville, Arkansas. The Brahman and Chianina steers had means of 61.9 and 17.0 horn flies per steer, respectively, during the fly season, whereas the Angus, Crossbred, Charolais and Red Poll steers had fly season means that ranged from 76.9 to 265.8 flies per steer. Regression analysis showed that an increase of 100 hairs per cm2, was associated with a reduction of 11 horn flies in the Angus II, 5 in Angus I, 20 in Charolais, 37 in Red Poll, and 0.4 in Chianina steers at the Savoy Station and a reduction of 6.6 horn flies for the Angus, Brahman, and Crossbred steers at the Booneville Centre. Regardless of cattle breed, an increase of 1.0 g of sebum per 929 cm2 output by the steer was associated with 478.5 additional hairs per cm2 on the animal. Each increase of 0.25 g of sebum per 929 cm2 resulted in a decrease of 9.2 horn flies per steer. We conclude that some of the factors responsible for fly‐resistance in cattle are hair density and the corresponding amount of sebum present on cattle skin and hair.

Population genetics of Amblyomma americanum (Acari: Ixodidae) collected from Arkansas.

ABSTRACT Lone star ticks, Amblyomma americanum L. (Acari: Ixodidae), infest multiple hosts such as birds, and mammals of various sizes (rodents to white-tailed deer) and can harbor human pathogens such as Borrelia lonestari and Ehrlichiosis chaffeensis. The population structure of 251 A. americanum ticks, collected from canines and two white-tailed deer in six Arkansas ecoregions, was examined using DNA sequences of a 247-bp region of the mitochondrial DNA ribosomal RNA 16S gene. Of the 247 nucleotide characters, 26 were variable. Thirty-three haplotypes were identified of which 25 haplotypes occurred once (10%). The most common haplotype was Aa25, occurring in 60% of the samples and found in all six ecoregions. The excess of low frequency haplotypes combined with the overall negative Tajimas D and Fu and Li statistics suggests population expansion. Phylogenetic relationships of the 33 A. americanum haplotypes were constructed with other Amblyomma species and identified A. americanum as a monophyletic species with two groups. The patterns of high nucleotide and haplotype diversity found in this study suggests that the A. americanum population is expanding perhaps due to its ability to survive in a variety of habitats and feed on multiple hosts. Given the gene flow in Arkansas, the spread of acaricide resistance and pathogens may be rapid.

Molecular Detection of Rickettsia Species within Ticks (Acari: Ixodidae) Collected from Arkansas United States

ABSTRACT Rocky Mountain spotted fever (RMSF), caused by the etiological agent Rickettsia rickettsii, is the most severe and frequently reported rickettsial illness in the United States, and is commonly diagnosed throughout the southeast. With the discoveries of Rickettsia parkeri and other spotted fever group rickettsiae (SFGR) in ticks, it remains inconclusive if the cases reported as RMSF are truly caused by R. rickettsii or other SFGR. Arkansas reports one of the highest incidence rates of RMSF in the country; consequently, to identify the rickettsiae in Arkansas, 1,731 ticks, 250 white-tailed deer, and 189 canines were screened by polymerase chain reaction (PCR) for the rickettsial genes gltA, rompB, and ompA. None of the white-tailed deer were positive, while two of the canines (1.1%) and 502 (29.0%) of the ticks were PCR positive. Five different tick species were PCR positive: 244 (37%) Amblyomma americanum L., 130 (38%) Ixodes scapularis Say, 65 (39%) Amblyomma maculatum (Koch), 30 (9%) Rhipicephalus sanguineus Latreille, 7 (4%) Dermacentor variabilis Say, and 26 (44%) unidentified Amblyomma ticks. None of the sequenced products were homologous to R. rickettsii. The most common Rickettsia via rompB amplification was Rickettsia montanensis and nonpathogenic Candidatus Rickettsia amblyommii, whereas with ompA amplification the most common Rickettsia was Ca. R. amblyommii. Many tick specimens collected in northwest Arkansas were PCR positive and these were commonly A. americanum harboring Ca. R. amblyommii, a currently nonpathogenic Rickettsia. Data reported here indicate that pathogenic R. rickettsii was absent from these ticks and suggest by extension that other SFGR are likely the causative agents for Arkansas diagnosed RMSF cases.

Genotype × Environment Interactions in Horn Fly (Diptera:Muscidae) Resistance in Angus, Brahman, and F1 Reciprocal Crossbred Cows on Common Bermudagrass or Endophyte-Infected Tail Fescue1

Weekly horn fly (Diptera:Muscidae) counts were recorded on 125 Angus, Brahman, and F1 reciprocal crossbred heifers grazing endophyte-infected tall fescue or common bermudagrass during the fly seasons in 1990 and 1991. Direct heterosis, maternal breed, and direct breed effects for average fly infestation were estimated as linear contrasts among sire breed × dam breed least squares means in these heifers. Heterosis differed between forages (P<.05) and averaged –16.8 (P<.01) and –.9 (P=.88) flies per head per d on common bermudagrass and tall fescue, respectively. Maternal breed effects were not significant on either forage. Direct breed effects favored the Brahman, were larger on common bermudagrass compared to tall fescue (P<. 10), and averaged –213.0 (P<.01) flies per head per d on common bermudagrass and –167.5 (P<.01) flies per head per d on tall fescue. The results suggested that utilization of heterosis and direct breed effects in Bos indicus × Bos taurus crossbreeding systems was effective in substantially lowering horn fly infestation, but the efficacy of the genetic effects depended on the forage environment.

Breed Means for Face Fly Count and Estimate of Heritability of Beef Cattle Resistance to the Face Fly1

Abstract Four hundred two observations of face fly count on 193 beef cows representing seven breed groups were used to obtain breed effects and estimate of heritability for cattle resistance to the face fly [Musca autumnalis (L.) Diptera: Muscidae]. Total face fly densities were determined weekly on each cow beginning in May and ending late October or early November of years 1988, 1989, and 1990. All fly counts were taken when cows were grazing Ozark upland native grass pastures with only containment fences separating breed groups. No insecticides were used in this study. Data for analysis were the mean annual face fly count for each cow. Breed and year effects were partitioned using an ANOVA with a split-plot design. The model used included an overall mean, breed, cow within breed, year, breed by year interaction, and a residual error. Breed, year, and interaction were significant (P 10 of x and the square root of x. This estimate suggests that beef cattle resistance to the face fly is largely under additive genetic control and that the possibility of selection procedures is an environmentally safe alternative to the use of insecticides.

Associations among heat shock protein 70 genotype, forage system, and horn-fly infestation of beef cattle

The objective of this experiment was to determine the relationships among cattle breed, heat shock protein 70 (Hsp70) genotype, and horn-fly density. Angus (n = 20), Brahman (n = 17), and reciprocal cross (n = 31) spring-born cows were assigned to 1 of 2 permanent forage types: wild-type endophyte-infected tall fescue [Lolium arundinaceum (Shreb.)] or common bermudagrass [Cynodon dactylon (L.) Pers]. Individual fly density was determined weekly at a distance of 5 to 10 m from May to October. Genomic DNA was prepared from buffy coat and purified. Specific forward and reverse PCR primers were used to produce Hsp70 amplicons of the coding (G2033C) and promoter (C895D and G1128T) regions. Each amplicon was sequenced, and genotypes were assigned to each single nucleotide polymorphism (SNP) site. Horn-fly density was affected (P < 0.0001) through a forage type-by-month interaction. In September, cattle grazing tall fescue had fewer flies (P < 0.05) than did cattle grazing bermudagrass. Heterozygous cows at the coding sequence SNP G2033C had more (P < 0.07) flies than did homozygous cows. Comparatively, cows heterozygous for either of the 2 promoter region SNP tended to have greater (P < 0.10) fly density than did those homozygous. Use of Hsp70 genotyping in combination with forage could be useful in identifying production systems that decrease horn-fly infestation.

Phylogenetics and population genetics of the louse fly, Lipoptena mazamae, from Arkansas, U.S.A.

Louse flies, also known as deer keds (Lipoptena mazamae Rondani), infest cervids such as white‐tailed deer, Odocoileus virginianus and vector pathogens such as Anaplasma and Bartonella schoenbuchensis to cattle and humans, respectively. The population genetic structure of 30 L. mazamae collected from white‐tailed deer in four regions of Arkansas, U.S.A., designated by county boundaries, was examined using DNA sequences of a 259‐bp region of the mitochondrial DNA rRNA 16S gene. Of the 259 nucleotide characters, 33 were variable and 6 haplotypes were identified. Two haplotypes occurred only once (haplotype 3 and 4), whereas two other haplotypes occurred in 43% (haplotype 1 in two regions) and 40% (haplotype 6 in three regions) of the samples. Phylogenetic relationships of the six L. mazamae haplotypes were constructed with other Hippoboscid and Glossinid samples and two clades resulted. Clade 1 was located in the north and western Ozarks whereas clade 2 was found in the northern and eastern Ozarks. Results from the present study indicate that Lipoptena may be a polyphyletic genus; consequently, more research into genetic variation within this genus is necessary.