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PubMed2006

Status of mastitis as an emerging disease in improved and periurban dairy farms in India.

While reviewing present status of mastitis in India, results of investigations from periurban dairy farms on epidemiological, clinical manifestations, diagnosis, bacterial isolation, in vitro drug sensitivity, and treatment of subclinical mastitis have been presented. Mastitis, on account of its causing serious wastage and undesirable milk quality, is emerging as a major challenge among the others (like breeding improvement, nutrition management, control of infectious, tick-borne, blood, and internal parasitic diseases) in dairy development of tropics. Subclinical mastitis was found more important in India (varying from 10-50% in cows and 5-20% in buffaloes) than clinical mastitis (1-10%). The incidence was highest in Purebred Holsteins and Jerseys and lowest in local cattle and buffaloes. An investigation on 250 animals from periurban farms indicated that the monsoon season was more prone to subclinical mastitis than summer or winter, prevalence increased with higher lactation number and animals in 4th-5th month of lactation were found more susceptible (59.49%), hind quarters were found more affected (56.52%) than fore quarters (43.47%). The factors like herd size, agro climatic conditions of the region, variations in sociocultural practices, milk marketing, literacy level of the animal owner, system of feeding, and management were found important affecting the incidence of subclinical mastitis. Comparison of efficacy of different diagnostic techniques for subclinical mastitis, such as modified California mastitis test (MCMT), bromo thymol blue (BTB), modified whiteside test, trypsin inhibition test, milk pH, and electric conductivity indicated MCMT to be most sensitive (95.16%) and specific (98.02%) test. The antimicrobial susceptibility test revealed that most of the bacterial strains (gram positive, gram negative, and mixed) isolated from subclinical mastitis milk samples, were highly sensitive to enrofloxacin 53.91%, least sensitive to oxytetracycline 17.39% and ampicillin 7.83%, and resistant to streptomycin. The therapy with enrofloxacin and nimesulide was found more efficacious (92.30%) in treating subclinical mastitis cows. It was concluded that consideration of socioecological factors for mastitis control in periurban area would help to reduce the cost of mastitis control in clean milk production.

Animals↗
PubMed2003

Prenatal exposure to testosterone increases ectoparasite susceptibility in the common lizard (Lacerta vivipara).

High levels of testosterone can benefit individual fitness, for example by increasing growth rate or ornament size, which may result in increased reproductive success. However, testosterone induces costs, such as a suppressed immune system, thereby generating trade-offs between growth or mate acquisition, and immunity. In birds and reptiles, females allocate steroids to their eggs, which may be a mechanism whereby females can influence the phenotype of their offspring. To our knowledge, only the benefits of early androgen exposure have been experimentally investigated to date. However, to understand this phenomenon, the costs also need to be evaluated. We manipulated testosterone levels in eggs of the viviparous common lizard and monitored growth, endurance and post-parturient responses to ectoparasites of the offspring. Testosterone-treated individuals had significantly higher growth rates than controls, but suffered a significant decrease in growth rate when exposed to ticks, whereas the corresponding difference for controls was non-significant. There was no difference in observed parasite load or leucocyte count between manipulated and control offspring. Thus, our results suggest that high testosterone levels during embryonic development have detrimental effects on immune function resulting in reduced growth rate, and that this must be taken into consideration when evaluating the potential adaptive value of maternal androgen allocation to eggs.

Analysis of Variance↗
PubMedDate not supplied

[A comparative evaluation of the sensitivity of the vector of tick-borne relapsing fever to pesticides by using the standard test paper].

Standard test paper, recommended by the WHO for the assessment of the arthropod sensitivity, was used to assess the sensitivity of Ornithodoros papillipes, the agent of tick-borne relapsing fever, to a number of pesticides widely used in or holding good promise for the agent control. Poor sensitivity of the tick to dieldrin, malathion, propoxur, bendiocarb (less than 40% of the ticks died after 1 h exposure), satisfactory sensitivity to DDT, and permetrin (60% of the ticks died), and very high sensitivity to deltametrin (100% death of the ticks) were revealed. The authors believe that the ticks will be similarly sensitive to other cyan-containing pyretroids.

Animals↗
PubMed1981

Response of hypersensitized guinea pigs to the feeding of Amblyomma americanum ticks.

Guinea pigs acquired resistance to the feeding of immature Amblyomma americanum ticks after a single infestation. The initial larval and nymphal feedings resulted in cumulative mortalities of 27.2 and 28.9%, respectively. The second and third larval infestations yielded cumulative mortalities of 50.5 and 52.4%, compared to 18.9 and 24.4% cumulative mortality from controls. Second and third nymphal feedings resulted in 75.7 and 73.4%, and ticks from controls exhibited 36.6 and 34.7% cumulative mortality. The development of host resistance adversely affected tick feeding and resulted in abnormally coloured ticks and a protracted moulting period with a marked decrease in moulting ability. Histological examination of tick feeding sites on guinea pigs challenged twice revealed greater cavity and lesion sizes in hosts fed upon by nymphs than larvae. The primary cell type within these feeding sites were basophils at 12 h post-attachment, but by 72 h post-attachment eosinophils were dominant. The upper epidermal layer adjacent to both larval and nymphal feeding ticks had accumulations of basophils with a few eosinophils. Lymphocytes may have been involved in the resistance response because local lymph nodes in resistant hosts were much larger than in uninfested and singly infested hosts. Some of these nodes had secondary germinal centres.

Animals↗
PubMed1981

Theileriosis in Uganda. Parasitological and serological responses in cattle continually exposed to natural infection.

Cattle living in a circumscribed area in Uganda, where both Theileria parva and T. mutans occurred naturally, were monitored for periods of up to 1 year by examination of blood and lymph node smears for parasites and the indirect fluorescent antibody test for antibodies to Theileria. Uninfected control cattle were added at intervals to ensure continuous challenge and to monitor the challenge. Although all 29 control animals became infected with T. parva, challenge was light at first as mortality from theileriosis only commenced in the 18 introduced after day 138 of the study; 14 of these died of the disease. Most of the 34 animals in the original group appeared to be susceptible to T. parva at the start of the study and 6 died of theileriosis. All animals were, or became, infected with T. mutans. Several animals exhibited patent T. parva infections on more than 1 occasion and 1 died from the second infection indicating the existence of immunologically different strains. Recovered animals appeared to acquire eventually a solid immunity to the local Theileria strains but 9 of the original animals and 7 of the controls died exhibiting massive tick and helminth burdens, sometimes aggravated by the effects of previous T. parva and/or T. mutans infections.

Animals↗
PubMed1993

Host genes, parasites and parasitic infections.

Resistance to infection of mammalian hosts by parasites is under genetic control at many different levels: between species, between races, breeds and lines of single species and between individuals. These genetic effects have been described in many host-parasite systems. Here we review the interaction between three elements: host genes, parasites and the environment in which parasitic infections develop. Already livestock industries exploit genetic variation between breeds, particularly for the control of trypanosomiasis and tick infestation in cattle. In most populations, and to many diseases, resistance is heritable and selective breeding for resistance in commercial livestock species has been successful experimentally. Attempts at utilizing genetic variation are placed in the broad context of the coevolution of host and parasite, the limited knowledge we have of the mode of action of resistance genes and our ability to use genetic information to predict resistance to parasites.

Animals↗
PubMed1988

Antigens and immunity in Theileria annulata.

About 200 million cattle are believed to be at risk from the debilitating and often fatal effects of tropical theileriosis, caused by Theileria annulata. Currently, there is no very cheap effective drug for treatment of T. annulata infections, although the hydroxynophthoquinones parvaquone and buparvaquone are reported to give good results(1-4). Control of the parasite principally involves vector control against the ixodid tick vectors - mainly by cattle dipping and spraying with acaricides - and vaccination using attenuated macroschizont-infected leucocytes (1-17) (see Box I). In this article, Roger Hall discusses the nature of immunity that can be achieved against T. annulata, and progress in identifying the main antigens involved in this immunity.

Journal Article↗
PubMed2006

A secreted cystatin from the tick Haemaphysalis longicornis and its distinct expression patterns in relation to innate immunity.

Proteins capable of selective and specific inhibition of cysteine protease have been identified as cystatins and are isolated from a variety of microbes and tissues of animals and plants. The physiological function of these proteins has been proposed to be the regulation of protein turnover and defense against pathogens as well as the balance of the host-parasite immune relationship. Genes encoding cystatins have been found in several species of ticks, but the function of cystatin in ticks is not understood. We cloned a gene encoding cystatin from tick H. longicornis and designated it as Hlcyst-2 (H. longicornis cystatin-2). Its full-length cDNA is 569 bp, and it encodes a putative 133 amino acid protein with an obvious signal peptide. Sequence analysis demonstrated that it has significant homology with the known cystatin. The recombinant protein was expressed in a GST-fused soluble form in Escherichia coli and purified by affinity chromatography. The inhibitory activity of the recombinant protein against papain, cathepsin L, and cathepsin B was identified by fluorogenic substrate analysis. Cystatin was mostly expressed in the tick midgut and hemocyte. Blood feeding induced significantly increased expression in the midgut. Real-time PCR confirmed that LPS-injected adult ticks expressed Hlcyst-2 1.6 more times than the PBS-injected control; Babesia gibsoni-infected larvae ticks expressed Hlcyst-2 1.8 more times than normal larvae ticks. The recombinant protein also showed a significant growth-inhibitory effect on Babesia bovis cultured in vitro. These results indicated this cystatin Hlcyst-2 is involved in tick innate immunity.

Amino Acid Sequence↗
PubMed2006

Comparison of the reproductive biology between acaricide-resistant and acaricide-susceptible Rhipicephalus (Boophilus) microplus (Acari: Ixodidae).

The reproductive fitness of Rhipicephalus (Boophilus) microplus (Canestrini) strains resistant to organophosphate (OP), pyrethroid (P), or formamidine (F) acaricides was compared to an acaricide-susceptible (SUS) strain to determine whether the acquisition of resistance affected reproductive fitness in the resistant strains. The SUS strain females had a 3.0 days preoviposition period, a 12.1 days oviposition period, a 22.5 days egg incubation period, a mean of 3670 eggs per female, and a mean percentage egg hatch of 78.1%, which were all remarkably similar to these same parameters reported for this species throughout the world. The reproductive biology of the P-resistant strain (PYR) and the F-resistant strain (FOR) were, for the most part, similar to those of the SUS strain. In the few instances where statistical differences did occur there was little evidence that the variation had any biological basis that could be attributed to a reduction in fitness related to resistance to P or F acaricides. Although the comparison of reproductive parameters of the OP-resistant strain (OPR) and the SUS strain identified statistical differences between the mean egg incubation and oviposition periods, the magnitude of the differences was not sufficient to conclude that the OPR strain was biologically less fit than the SUS strain. However, the OPR strain produced 30% fewer eggs (2562 eggs per female) than the SUS strain (3670 eggs per female) indicating the acquisition of resistance placed the OPR at a selective disadvantage relative to the SUS strain. This coupled with a lower, though non-significant, egg hatch was used to predict there would be a reduction of at least 34.1% in larval numbers available to potentially re-infest subsequent cattle than were available from the SUS strain. These data may aid the development of management strategies that can be used to control OP-resistant ticks.

Amidines↗
PubMed2002

Evidence of an assembly pheromone in the black-legged deer tick, Ixodes scapularis.

The responses of Irodes scapularis (Acari: Ixodidae) nymphs and adults to extracts of cast larval skins were tested in a Petri dish bioassay. Assembly was elicited in nymphs and adults in the presence of skins, exudate from ticks, and filter paper exposed to ticks compared to untreated controls. Assembly was noted by 1 hr after exposure with little change between 1 and 24 hr. The assembly response increased in the presence of an increased number of skins. Similar assembly was elicited in nymphs and adults in the presence of cast larval skins and a saline (0.95% NaCl) skin extract. Methanol and hexane extracts were not attractive. When chemical standards were tested against nymphs, they responded to guanine, uric acid, hypoxanthine, xanthine, inosine, and hematin. Adults were tested against guanine, inosine, and xanthine, and all elicited significant assembly. Responses of nymphs increased significantly with increase in dose of uric acid and guanine. Responses of nymphs to a mixture of guanine, xanthine, and adenine (25:1:1 ratio) were similar to responses to cast skins. This study provides the first evidence of an assembly pheromone in I. scapularis.

Animals↗
PubMed1980

Action of formamidine pesticides on octopamine receptors.

The formamidines are a structurally novel group of pesticides of growing importance in the control of mites, cattle ticks and certain orders of insects which have become resistant to conventional acaricides and insecticides. Their mode of action is complex with dose-dependent lethal and subletahal effects. At sublethal levels they cause behavioural changes in the target pest species (for example in feeding and in mating behaviours), changes which are responsible for the protective effects on crops and livestock. Although many suggestions have been made for the underlying biochemical mechanism, including inhibition of monoamine oxidase activity, uncoupling of respiration and blockade of neuromuscular transmission, no direct evidence has been presented. Another possibility is interaction with octopamine receptors in the central nervous system. We report here that the formamidine acaricide/insecticide, chlordimeform (CDM), and its demethylated deivative can mimic the actions of octopamine at the locust neuromuscular junctions. This gives the clearest evidence to date of the site of action of the formamidines and indicates a novel mode of action for these pesticides.

Amidines↗
PubMed1981

Carcinogenicity of dichlorvos.

Dichlorvos, 2,2-dichlorovinyl dimethyl phosphate, an organophosphate insecticide, is widely used for the control of agricultural, industrial, and domestic pests (Fig. 1) [1]. Dichlorvos is administered orally as an anthelmintic to swine, horses, cats, and dogs. It is applied by dermal application to cattle, goats, sheep, swine, and chickens to control fleas, flies, and mites. Cucumbers, radishes, lettuce, and tomatoes are treated with dichlorvos in greenhouses. Aerosols and strips are used for the control of ants, bedbugs, ticks, cockroaches, flies, mosquitoes, silverfish, spiders, and wasps. Exposure to dichlorvos is by the inhalation of sprays or vapors from impregnated resins, by skin contact, or orally as a residue in food. The predominant mode of toxicity of dichlorvos is inhibition of cholinesterase. This review includes, to the best of our knowledge, every study on the carcinogenicity of dichlorvos in animals. The studies reviewed are: NCI Dichlorvos Rat Study, Tunstall Laboratory Dichlorvos Rat Study, Kettering Laboratory Dichlorvos Rat Study, Kettering Laboratory Dichlorvos Dog Study, Shell Chemical Company Dichlorvos Swine Study, and NCI Dichlorvos Mouse Study. The conclusions from the NCI Dichlorvos Rat Study and the NCI Dichlorvos Mouse Study are based on my examination and diagnosis of the histological sections. Statistical tests of significance were obtained with Fisher's exact test, and tests for positive linear trend and departure from linear trend.

Adenoma↗
PubMed2005

New ruminant hosts and wider geographic range identified for Babesia odocoilei (Emerson and Wright 1970).

Babesia odocoilei was found to infect two previously unknown host species, desert bighorn sheep (Ovis canadensis nelsoni) and musk oxen (Ovibos moschatus), both of which are members of the family Bovidae. Previously, B. odocoilei has been reported in only Cervidae hosts. New geographic regions where B. odocoilei infections have not been reported previously include Pennsylvania and New York, where fatal babesiosis has occurred in reindeer (Rangifer tarandus tarandus); New Hampshire, where elk (Cervus elaphus canadensis) have been affected; and California, home of the infected desert bighorn sheep. Infection with B. odocoilei in these hosts was confirmed by parasite small subunit ribosomal RNA gene sequence analysis. A serosurvey for B. odocoilei antibody activity in New Hampshire showed prevalence rates of 100% at two elk farms and 12% at another farm. Control of potential vector ticks, Ixodes scapularis, especially when translocating livestock, is imperative to prevent outbreaks of babesiosis in managed herds of potential host species.

Animals↗
PubMed2001

Integrated pest management and allocation of control efforts for vector-borne diseases.

Applications of various control methods were evaluated to determine how to integrate methods so as to minimize the number of human cases of vector-borne diseases. These diseases can be controlled by lowering the number of vector-human contacts (e.g., by pesticide applications or use of repellents), or by lowering the proportion of vectors infected with pathogens (e.g., by lowering or vaccinating reservoir host populations). Control methods should be combined in such a way as to most efficiently lower the probability of human encounter with an infected vector. Simulations using a simple probabilistic model of pathogen transmission suggest that the most efficient way to integrate different control methods is to combine methods that have the same effect (e.g., combine treatments that lower the vector population; or combine treatments that lower pathogen prevalence in vectors). Combining techniques that have different effects (e.g., a technique that lowers vector populations with a technique that lowers pathogen prevalence in vectors) will be less efficient than combining two techniques that both lower vector populations or combining two techniques that both lower pathogen prevalence, costs being the same. Costs of alternative control methods generally differ, so the efficiency of various combinations at lowering human contact with infected vectors should be estimated at available funding levels. Data should be collected from initial trials to improve the effects of subsequent interventions on the number of human cases.

Animals↗
PubMed1975

Canine ehrlichiosis (tropical canine pancytopenia) in Thailand.

An epizootic of canine ehrlichiosis has occurred in military working dogs in Thailand. During the epizootic, 161 cases of ehrlichiosis were identified serologically in a population of 316 dogs, and 54 dogs exhibited clinical signs of disease. The epizootic is being controlled by elimination of ticks, by serologic identification and treatment of carriers with 30 mg/lb body weight/day of tetracycline for 14 days, and by continuous daily prophylactic administration of 3 mg/lb body weight/day of tetracycline. Clinical and serologic recognition of ehrlichiosis among pet dogs in widely separated regions of Thailand suggest that the disease has been endemic in Thailand for an extended time. Under such circumstances it is possible that pet and stray dogs have served as a source of infection for the epizootic in military working dogs.

Animals↗