Vitreous humor analysis for selected biochemical parameters from cervids in Idaho.

Vitreous humor and liver samples were collected from hunter-harvested elk (Cervus elaphus) and mule deer (Odocoileus hemionus) in Idaho (USA). Concentrations of calcium, chloride, potassium, sodium, urea nitrogen and selenium were determined and evaluated according to species, age, gender, geographic location, and time elapsed following death. Vitreous humor analysis yielded reliable biochemical information for < or = 96 hr subsequent to the death of the animal. Vitreous potassium concentration changes over time could be used to estimate the time that elapsed following death.

Susceptibility of elk (Cervus elaphus) to experimental infection with Anaplasma marginale and A. ovis.

Anaplasma ovis was experimentally transmitted from domestic sheep to elk (Cervus elaphus) and back to splenectomized sheep. No rickettsemias were detected but serum from three of seven experimentally inoculated elk developed Anaplasma spp.-reactive antibody as measured by indirect immunofluorescence (IIF) or by the rapid card agglutination and complement fixation assays. Three elk were experimentally infected with A. marginale. The rickettsiae were detected in blood of these elk and caused disease in a splenectomized domestic bovine calf after subinoculation of blood from the elk. All three elk had positive titers with IIF. No clinical signs of illness were noted in any elk inoculated with either Anaplasma species.

Hematologic, serologic values, histopathologic and fecal evaluations of bison from Yellowstone Park.

Hematologic and blood chemistry parameters were measured in 149 free-ranging American bison (Bison bison) from Yellowstone National Park, Wyoming (USA). Additionally, histopathologic evaluations of lung, liver, spleen, kidney, and mesenteric and bronchial lymph nodes were made from ten animals. Forty-five fecal samples were screened for the presence of helminth ova. Leukopenia and markedly low blood urea nitrogen concentrations were the most notable differences observed from other bison populations. All tissues examined were essentially normal; there was evidence of moderate intestinal parasite burdens.

Efficacy of buparvaquone as a therapeutic and clearing agent of Babesia equi of European origin in horses.

We evaluated the efficacy of buparvaquone in eliminating infection with Babesia equi of European origin in carrier horses and in splenectomized horses with experimentally induced acute infection. When administered at the rate of 5 mg/kg of body weight, IV, 4 times at 48-hour intervals, buparvaquone prompted rapid abatement of parasitemia. However, secondary and tertiary recrudescent parasitemias invariably returned with establishment of the carrier state. Buparvaquone, at the dosage evaluated, had transitory therapeutic efficacy against acute B equi infection in splenectomized horses, but was unable alone to clear carrier infection.

Seasonality of natural transmission of bovine anaplasmosis under desert mountain range conditions.

Splenectomized cattle and mature, spleen-intact cattle were used as sentinels in a 4-year study to assess the seasonality of naturally transmitted anaplasmosis. Sentinels were exchanged and/or monitored monthly on 4 study areas of desert mountain range land in Idaho, Oregon, and Utah. Acute Anaplasma infections were diagnosed in sentinels every month of the year. Of 44 total infections, 29 (66%) were detected during March through August, the primary arthropod season. From December through February, 8 (18%) of the total 44 Anaplasma infections were diagnosed; the winter tick, Dermacentor albipictus, was the probable disease vector. Susceptible cattle were determined to be at risk throughout the year, and anaplasmosis should be considered as a possible diagnosis in cattle with anemia during any season.

Evaluations of buparvaquone as a treatment for equine babesiosis (Babesia equi).

We evaluated the efficacy of buparvaquone in eliminating Babesia equi of European origin in carrier horses and in experimentally infected splenectomized ponies. When administered at the rate of 2.5 mg/kg of body weight, IM, 4 times at 96-hour intervals, buparvaquone was effective in eliminating B equi carrier infection in 1 horse. Such results could not be repeated at the same dosage or at 3.5 or 5 mg/kg, IM. Buparvaquone given at the rate of 4 to 6 mg/kg IV and/or IM was therapeutically effective in 4 of 5 acute B equi infections in splenectomized ponies. The treated ponies became carriers.

Characteristics of an attenuated Anaplasma marginale of deer origin as an anaplasmosis vaccine.

A fully virulent field Anaplasma marginale isolate, passaged to a splenectomised white tailed deer, lost virulence for cattle after 18 months in the non-bovine host. This attenuated A. marginale produced a mild response in four 18-month-old Holstein steers characterised by an average 2.4% parasitaemia, a 13% drop in PCV and a positive serological response. All vaccinated steers were immune to challenge with a fully virulent, heterologous A. marginale when compared with non-vaccinated controls.

The pathogenicity and immunologic relationship of a virulent and a tissue-culture-adapted Babesia bovis.

Babesia bovis grown in tissue culture was used to inoculate 12, 2-year-old Holstein steers. All 12 developed serological evidence of infection but only six had a febrile response of greater than or equal to 40 degrees C, and only one had a demonstrable B. bovis parasitemia. An average modest drop of 19% was observed in packed cell volume (PCV) during the period of reaction. All 12 steers were subsequently challenged with virulent B. bovis: seven on day 78 post inoculation (p.i.), two on day 106 p.i., and three on day 251 p.i. No demonstrable clinical response was observed in any of the 12 steers previously exposed to the tissue-culture organism, whereas severe signs of babesiosis occurred in seven 2-year-old, non-vaccinated control steers given a comparably virulent B. bovis challenge. All seven controls showed a febrile response, B. bovis parasitemias, with an average drop of 55% in PCV and a 28% mortality.

Experimental anaplasmosis in mule deer: persistence of infection of Anaplasma marginale and susceptibility to A. ovis.

An experimental Anaplasma marginale infection was induced in a splenectomized mule deer (Odocoileus hemionus hemionus) which persisted subclinically at least 376 days as detected by subinoculation into susceptible cattle. Anaplasma ovis was experimentally transmitted from sheep to a splenectomized and a spleen-intact mule deer, and back to sheep. The pathogenesis in deer was very similar to that seen in sheep using ovine blood inoculations.

Imidocarb and parvaquone in the treatment of piroplasmosis (Babesia equi) in equids.

The therapeutic efficacies of imidocarb and parvaquone were tested against Babesia equi of European origin in carrier horses and for induced acute infections in splenectomized ponies. Imidocarb, at a dosage of 4 mg/kg of body weight, given IM at 72-hour intervals 4 times, was ineffective in eliminating B equi-carrier infection in 9 mature geldings. A single IM administration of 4 mg/kg was not therapeutic in acutely infected splenectomized ponies. When given at 3 different dosages and treatment schedules, parvaquone was ineffective in clearing carrier infection. Parvaquone given IM once at a dosage of 20 mg/kg was effective for acute B equi infections in splenectomized ponies; parasitemia began to decrease within 24 hours after treatment. Infections were not eliminated however, and within 4 weeks, secondary parasitemia and anemia developed. Of 4 ponies, 3 died of acute piroplasmosis.

Experimental infections of Anaplasma ovis in pronghorn antelope.

Anaplasma ovis was experimentally transmitted from sheep to pronghorn antelope (Antilocapra americana) and back to sheep. Anaplasma ovis was recovered in splenectomized sheep, from two of three spleen-intact pronghorns following their inoculation with blood from known A. ovis carrier sheep. These two pronghorns exhibited a 0.5% or higher A. ovis parasitemia within 48 days after exposure, and an anaplasmosis-positive serological response 91 days after exposure. Clinical signs of illness were not observed. Blood from the infected pronghorns produced disease in four splenectomized sheep.

Ovine anaplasmosis: in utero transmission as it relates to stage of gestation.

Seventeen mature, pregnant, anaplasmosis-susceptible and 3 anaplasmosis-carrier ewes were used in Anaplasma ovis in utero transmission studies. Susceptible ewes were arbitrarily allotted to 3 groups, 4 each in groups A and C and 9 in group B, and were inoculated with whole blood from a carrier ewe. Each group was Anaplasma-exposed once during one of the thirds of pregnancy. In all ewes, resulting parasitemias were low and anemias were mild. Three carrier ewes comprised group D. Blood samples were obtained once during gestation from each fetus at various stages of development for evaluation and inoculation into splenectomized lambs. Blood obtained from neonates before nursing was also evaluated for Anaplasma presence. Parasitemia was not detected in any fetus or neonate; however, 3 of 16 splenectomized lambs inoculated with fetal or neonate blood developed acute anaplasmosis. Dams of fetuses/neonates with infective blood had been Anaplasma-exposed during their 2nd or last 3rd of pregnancy. Infective Anaplasma agents crossed the placental barrier as early as 130 days of gestation.

Experimental infections of Babesia bigemina in American bison.

Babesia bigemina was experimentally transmitted from cattle to bison and back to cattle. One spleen-intact and two splenectomized American bison (Bison bison) inoculated with a B. bigemina stabilate exhibited clinical and hematological signs of babesiosis within 10 days of exposure. Blood from the infected bison produced disease in a splenectomized bovine steer.

Bovine anaplasmosis: susceptibility of seronegative cows from an infected herd to experimental infection with Anaplasma marginale.

Adult cows from an Anaplasma marginale-infected herd that were negative to the A marginale rapid card agglutination (RCA) and complement fixation (CF) tests for 1 to 4 years developed acute anaplasmosis after inoculation with 0.5 ml of blood from an A marginale carrier cow. The test cattle were as susceptible as the control cattle of similar ages. Also, 2 cows that had seroconverted from RCA/CF-positive to RCA/CF-negative status naturally were fully susceptible to anaplasmosis when they were experimentally infected. Results of the study indicated that indigenous seronegative cattle in anaplasmosis-enzootic regions probably do not have acquired or natural immunity to A marginale infection.

Transmission of Anaplasma marginale Theiler by males of Dermacentor andersoni Stiles fed on an Idaho field-infected, chronic carrier cow.

The role of ticks and carrier cattle in epizootics of bovine anaplasmosis was further clarified by demonstrating unequivocally, for the first time, that male ticks fed on a chronic carrier cow naturally infected with Anaplasma marginale can transmit this parasite intrastadially and biologically when subsequently fed on susceptible cattle. These data indicate that field epizootics of acute anaplasmosis may be initiated by males of tick vector species that feed on carrier cattle and subsequently transfer to susceptible cattle.

Test of the sheep ked Melophagus ovinus (L) as a vector of Anaplasma ovis Lestoquard.

The sheep ked Melophagus ovinus was evaluated as a possible vector of Anaplasma ovis. In 4 tests, 45 to 293 keds were transferred from sheep with acute anaplasmosis, low level parasitemia, or carrier state of anaplasmosis to individual splenectomized ewes. Keds were confined in stockinette cages attached to the dorsal midline of the recipient hosts for 10 days. Throughout the 90-day observation periods after the keds were transferred, no clinical, serologic, or hematologic evidence of anaplasmosis was detected in any of the ked-recipient ewes. Results indicate that sheep keds probably are not mechanical or biological vectors of the ovine anaplasmosis organism.

Experimental anaplasmosis in American bison: persistence of infections of Anaplasma marginale and non-susceptibility to A. ovis.

Blood collected 314 and 496 days after experimentally infecting splenectomized and spleen-intact American bison (Bison bison) with Anaplasma marginale was infective for splenectomized bovine steers. The pathogenesis was identical to that seen in bovine studies using bovine blood inoculations. A splenectomized bison remained normal clinically, hematologically and serologically for 10 mo after repeated inoculation of ovine blood infected with A. ovis.

Epidemiologic aspects of bovine anaplasmosis in semiarid range conditions of south central Idaho.

The prevalance of Anaplasma marginale-infected cows, as determined by use of the modified rapid card agglutination (MRCA) test, was measured during a 4-year period (1980-1983). The prevalence of A marginale-infected cows, defined as positive reactors on the MRCA test, remained constant (31%-37%). The apparent incidence of A marginale transmission to susceptible cows was approximately 7% from 1980 to 1981, 8% from 1981 to 1982, and no transmission from 1982 to 1983. The occasional MRCA-positive cow became negative on the MRCA test, and 1 cow was determined to be free of A marginale infection by subinoculation of 100 ml of the cow's blood into a susceptible, splenectomized calf. Dermacentor andersoni, a known vector of A marginale, was often found on the cattle and in their environment. However, A marginale was not transmitted to susceptible, splenectomized calves, using collected ticks. Of 56 calves born to MRCA-positive cows, 82% were MRCA-positive within the first 3 months of life. These calves converted to MRCA-negative status and were determined to be free of A marginale infection by subinoculation of their blood into susceptible, splenectomized calves, indicating the passive transfer of colostral antibodies.

Bovine anaplasmosis: transplacental transmission as it relates to stage of gestation.

Six mature, pregnant, anaplasmosis-susceptible and 3 anaplasmosis-carrier beef cows were used in Anaplasma in utero transmission studies. Susceptible cows were randomly allotted into 3 groups of 2 cows each and were inoculated with a Virginia A marginale stabilate. Each group was Anaplasma-exposed once during 1 of the 3 trimesters of pregnancy. Blood samples were obtained from each fetus at various stages of development for evaluation and for subinoculation into splenectomized calves once during gestation. Precolostral blood from neonates was also subinoculated into individual susceptible calves. Two of the 9 splenectomized calves given fetal blood inoculations developed acute anaplasmosis. The dam of 1 fetus with infective blood was Anaplasma-exposed during the 2nd trimester of pregnancy, and the dam of the second fetus was exposed during her 3rd trimester. Infective fetal blood was obtained during the same trimester of gestation in which the dams were inoculated. Calves given neonatal precolostral blood did not develop anaplasmosis.