Fred C. Wright

Cross-Mating Studies with Psoroptes ovis (Hering) and Psoroptes cuniculi Delafond (Acarina: Psoroptidae)

Reciprocal cross-matings of Psoroptes ovis and P. cuniculi occurred and produced viable offspring through the F2 generation. Hybrids of these crosses were infective to both rabbits and cattle. Mean lengths of the male l4 setae of the parental species differed significantly from each other as well as from those of the hybrid males. These data show that P. ovis and P. cuniculi are not reproductively isolated. Because viable, fertile hybrids are produced, cross-matings of P. ovis and P. cuniculi are not suitable as a suppression method of cattle scabies.

Comparison of Lengths of Outer Opisthosomal Setae of Male Psoroptic Mites Collected from Various Hosts

Sweatman (1958, Can. J. Zool. 36: 905-929) reported that the location of Psoroptes mites on the host animal, i.e., ear or body, was one of the determining factors for separation of the psoroptic mites into species. He also confirmed the observation of Hirst (1922, Brit. Museum Nat. History, Econ. Ser. No. 13) that the setae on the opisthosomal lobes of the adult male were of diagnostic value. Sweatman concluded that the outer opisthosomal setae (OOS) or 14 setae (Fain, 1970, Rev. Zool. Bot. Afr. LXXXI: 95-100) was the primary factor in separation of the species and that Psoroptes ovis and P. bovis were the same species even though the host animals were different. Observations in our laboratory have indicated a wide overlap in the lengths of the 14 setae of adult males of psoroptic mites in our collections from various hosts and geographic locations. Sweatman also noted this overlap. The objective of our study was to compare lengths of the 14 setae of male psoroptic mites collected from various hosts from different geographic locations and to determine the reliability of the length of 14 setae as a characteristic to differentiate between species. Most of the mites studied were collected in recent years; however, additional mounted specimens were obtained from the collection of the Parasite Research Laboratory, Albuquerque, New Mexico, now located at Kerrville, Texas, as the Scabies and Mange Mite Research Unit of the U.S. Livestock Insects Laboratory. Mites collected from the ears of rabbits, goats, mule deer, white-tail deer, and ibex were considered to be P. cuniculi. Mites collected from the body of cattle and domestic sheep were considered to be P. ovis. Mites collected from bighorn sheep were considered to be P. ovis or P. cervinus. The mites were mounted on glass slides in Hoyers medium for measurements. Setal length was measured in micrometers (,um) with a Zeiss microscope equipped with differential interference-contrast, x 10 eye pieces, a x 40 objective, and a calibrated measuring reticule. Each 14 seta measured was considered an observation. Data were transformed to log 10 values and analyzed by one-way analysis of variance (ANOVA) for unequal sample sizes (Sokal and Rohlf, 1969, W. H. Freeman and Co., San Francisco, California, 776 p.). The differences between the means of the lengths of the 14 setae from the mites from various collections were analyzed by the Student-Neuman-Keuls (SNK) test for unequal sample sizes (Sokal and Rohlf, 1969, loc. cit.). The log 10 mean values were converted to their antilog value before being reported in the test. The lengths of the 14 setae of the adult male mites of Psoroptes spp. collected from the various hosts and geographic locations were compared statistically (Table I). The lengths of the 14 setae of mites (Mission strain) collected from sheep, of mites from bighorn sheep (Idaho), and of mites from cattle (Brazil) were all significantly different (P < 0.05) from the lengths of 14 setae from all other collections of mites regardless of host, body location, or geographic location. There were many differences within the same host animal. For example, the lengths of 14 setae from mites collected from rabbits from New Mexico, Kerrville, and England were all significantly different from each other. The lengths of 14 setae of mites collected from goats in Texas and New Mexico were significantly different from each other. The lengths of 14 setae of mites collected from cattle in the USA (Albuquerque, Kerrville, Hereford, and Colorado) were significantly different (P < 0.05) from those of mites collected from Holstein cattle from Brazil. The lengths of 14 setae from mites of the Mission strain from sheep were significantly different from those of all other strains of mites from sheep at Albuquerque, England, and South Africa. The lengths of 14 setae from mites of the mixed strain and the ADP strain were significantly different from those of the Beltsville-2 strain and England strain also. There was no consistency between the

Preliminary trials using a macrocyclic lactone against psoroptic scabies of cattle

A macrocyclic lactone, LL-F28249 alpha, C36H52O8, was evaluated as a one- or two-injection treatment in different formulations and concentrations against cattle infested with Psoroptes ovis (Hering). One injection of 2 mg kg-1 or two injections of 1 mg kg-1 of 3% active material in either an aqueous or oil formulation failed to eliminate all of the mites. A single injection of 3 mg kg-1 as a 5% aqueous formulation eliminated all mites for 35 days post-injection. At lower dosages of the aqueous formulation (3%), the male mites appeared to be less susceptible to the acaricide than either the female or immature mites.

Effect of age on cholinesterase activity and protein of unfed larval ticks

The cholinesterase (AChE) activity and total protein in homogenates of unfed larvae of Amblyomma americanum (L.), A. cajennense (Fabricius), A. maculatum Koch, Anocentor nitens Neumann, and Boophilus microplus (Canestrini) were determined weekly in ticks 1-6 wk of age. There was a considerable variation in total protein, AChE, and the ratio of AChE to protein as the ticks aged. However, AChE activities were constant or increased with age and total protein levels were constant or decreased. No direct relationship was detected between AChE activity and total protein levels. The ratio of AChE to protein increased as the unfed larval ticks aged.

Control of psoroptic scabies cattle with fenvalerate

Fenvalerate [Cyano(3-phenoxyphenyl)methyl-4-chloro-alpha-(1-methylethyl) benzene acetate] was evaluated as a one- or two-dip treatment at two different concentrations against cattle infested with Psoroptes ovis (Hering). One or two dips at 0.025% or one dip at 0.05% failed to eliminate P. ovis; two dips in fenvalerate at 0.05% provided complete elimination of all mites. Fenvalerate was equally effective against male, female, and immature mites, but did not exhibit ovicidal properties.