The ranging behaviour and habitat use of rabbits on farmland and their potential role in the epidemiology of paratuberculosis

Grazing herbivores avoid grass swards contaminated with faeces as the ingestion of faeces is a common route of micro- and macro-parasite transmission. The recent novel finding that herbivores do not avoid grass swards contaminated with rabbit faeces suggests that disease risk posed to herbivores by rabbits is determined by rabbit ranging and excretory behaviour. Using as a case study rabbits and the risk Mycobacterium avium sub-species paratuberculosis (M. a. paratuberculosis) poses to cattle, the interaction between rabbits and grazing pasture was studied on an infected farm in the east of Scotland in spring and autumn 2000. Radio telemetry, burrow surveys and faecal pellet count data were collected on two areas (Areas 1 and 2) of the farm with different habitat mosaics, to study the potential effects of season and habitat on the spatial distribution of rabbits faeces and thus disease in the environment. Twenty one rabbits were radio tracked and a total of 902 fixes collected. Mean home range sizes (100% minimum convex polygons) were between 2.0 and 7.1 ha per rabbit per season. Home ranges were significantly larger in spring, and in Area 1 which had more moor and woodland and less rough pasture. Rabbits used rough pasture most in Area 1 and gorse scrub in Area 2. In both areas, significantly more burrows were located in gorse scrub than in any other habitat. Most faecal pellets were deposited on the moorland habitat of Area 2 in autumn. In habitats to which grazing livestock had access, the mean rate of faecal deposition was 8571 pellets per ha per day. The greatest risk of disease transmission occurred in habitats of poor grazing quality (e.g., gorse scrub) which were used by rabbits for burrowing and thus contained high concentrations of faeces. The findings of the study are discussed in relation to management practices aimed at reducing disease risk to livestock, including the fencing of scrub and the reduction of rabbit population size to prevent expansion of rabbit burrows from scrub into grazing pastures.     

The use of epidemiology to enhance production animal research

The approach to understanding the impact of management and disease in production animal systems has evolved with the advent of both routine on-farm data collection and new analytic epidemiology techniques. Epidemiology provides a tool to describe the host-agent-environment triad and the impact of multiple variables on productivity and health recognized by production animal veterinarians in their day-to-day work. Field trials enable veterinarians to systematically test whether or not a new treatment improves the health of the animal populations in their geographic region and under their production systems. Hypothesis-specific coding techniques, such as hierarchical variables, are used in a systematic manner to understand well-defined biological phenomenon. Clustering at multiple levels has provided the challenges of measuring management changes in each level. Using random effects models allow us to determine the relative importance of each level on the dependent variable. As epidemiologists, we have taken advantage of analytic techniques used in other fields of science. Geo-spatial statistics has been used to understand the clustering and spread of diseases and more recently, to interpret the laboratory findings related to the introduction of an exotic strain of the influenza virus. Dr. Martin, through his work as a veterinary epidemiologist and that of people he has influenced, has been an international leader in promoting the optimal health and productivity of animal populations and of ensuring the safety of foods of animal origin and preventing animal-related disease in humans.     

Complex epidemiology and zoonotic potential for Cryptosporidium suis in rural Madagascar

Cryptosporidium spp. is the most important parasitic diarrheal agent in the world, is among the top four causes of moderate-to-severe diarrheal disease in young children in developing nations, and is problematic as an opportunistic co-infection with HIV. In addition, Cryptosporidium is a persistent challenge for livestock production. Despite its zoonotic potential, few studies have examined the ecology and epidemiology of this pathogen in rural systems characterized by high rates of overlap among humans, domesticated animals, and wildlife. To improve our understanding of the zoonotic potential of Cryptosporidium species in the rural tropics, we screened humans, livestock, peridomestic rodents, and wildlife using PCR-RFLP and sequencing-based approaches to distinguish species of Cryptosporidium in rural southeastern Madagascar. Cryptosporidium of multiple species/genotypes were apparent in this study system. Interestingly, C. suis was the dominant species of Cryptosporidium in the region, infecting humans (n = 1), cattle (n =  18), pigs (n= 3), and rodents (n = 1). The broad species range of C. suis and the lack of common cattle Cryptosporidium species (Cryptosporidium parvum and Cryptosporidium andersoni) in this system are unique. This report represents the fifth confirmed case of C. suis infection in humans, and the first case in Africa. Few rural human and livestock populations have been screened for Cryptosporidium using genus-specific genotyping methods. Consequently, C. suis may be more widespread in human and cattle populations than previously believed.     

The biology of dendritic cells and their potential use in veterinary medicine

Dendritic cells have been shown to be the main antigen-presenting cells in vitro and in vivo, playing a pivotal role in the induction of both tolerance and immunity. Dendritic cells from humans and mice have been extensively studied and dendritic cell-based vaccines have been shown to be effective in the prevention and treatment of infectious, allergic and neoplastic diseases. Studies of dendritic cells of domestic animal origin are becoming available and confirm a role for these cells in the pathogenesis of a variety of animal diseases, suggesting that dendritic cells could be used as adjuvants for prophylactic and therapeutic strategies in veterinary medicine.     

The epidemiology of fascioliasis in Malawi: I. The epidemiology in the intermediate host

Fasciola gigantica Cobbold was studied in the intermediate host snail. On snail survey Lymnaea natalensis Krauss was the species found responsible for the transmission of Fasciola gigantica in Malawi. The ecology of this snail was studied at 5 different habitats spread throughout Malawi. The snail population was recorded high from April to October. The epidemiological cycle of Fasciola gigantica in the snail was determined and it was shown that snail infection was high in April and May and thus more metacercariae are released in August to October following such an infection. To complete the epidemiological picture studies reported separately were done involving the definitive host.     

The use of pulsed-field gel electrophoresis to investigate the epidemiology of Mycoplasma bovis in French calf feedlots

Mycoplasma bovis is a major cause of respiratory outbreaks in cattle feedlots. In this study pulsed-field gel electrophoresis (PFGE) was used to trace field strains and provide information on M. bovis patterns of spread in calf feedlots. The suitability of KpnI, MluI and SmaI restriction enzymes was assessed on different sets of strains. The discriminative power of the first two enzymes was first assessed using 28 epidemiologically unrelated strains; stability was 100% on multiple isolates from in vivo experimental infection. Thirty-nine field isolates from six feedlots were then evaluated. In contrast to the unique fingerprints displayed by the unrelated strains, the isolates from the feedlots showed identical patterns at the time of the outbreak of respiratory disease and 4 weeks later. The PFGE typing results suggest that M. bovis strains follow a clonal epidemic spread pattern at the herd level and that the same strain persists in calves of the herd after the clinical signs have disappeared.     

The epidemiology of bluetongue

The perception that bluetongue virus (BTV), once introduced to a country, would decimate its sheep industry, grew from the acceptance in the late 1950s that it was an emerging virus with Africa as its source. Epidemiological studies in the 1960s and early 1970s confirmed that the geographic distribution of BTV infections included regions of the world, outside the traditionally defined areas where BT was observed. This was interpreted at the time as representing serious and rapid spread of the virus.

This review provides evidence to rebut this earlier view. What has emerged through the 1980s is: (a) the recognition that BTV is a common infection of ruminant livestock throughout the tropics and sub-tropics apparently within several separate ecosystems; (b) in most areas of the world, infection is sub-clinical; (c) incursions of virus (with accompanying disease) into temperate climates do occur at certain key locations, but “die out” usually within the same year; (d) recognition of the vector competence of Culicoides spp in the different ecosystems of the world is critical for understanding the epidemiology of disease; (e) persistent infection in ruminants is no longer considered important in the long term perpetuation of the virus.     

The potential for liability in the use and misuse of veterinary vaccines.

The lack of specific rules regarding the use of animal vaccines by veterinarians leaves them vulnerable to legal action for negligence or breach of warranty. A veterinarian's liability may depend on the answers to the questions asked previously in this article. The answers ultimately depend on the specific circumstances of the case. Although no one can ensure that he or she is never going to be sued, veterinarians can go a long way in defending themselves against these kinds of allegations by conforming to the standards of practice as they apply to the care and use of vaccines; by adhering closely to the doctrines of informed consent; and by not providing undue warranty to the vaccine product he or she sells.     

The epidemiology of animal trichinellosis in China

The epidemiology of animal trichinellosis in China based mainly upon original Chinese literature published between 1937 and 2004 is reviewed. The seroprevalence of Trichinella infection in herbivores was 0.7% (2/300) in cattle and 0.8% (4/500) in sheep. The prevalence of trichinellosis in naturally infected cattle was 1.2% (2/163). Trichinella larvae were detected in 1.4% (3/215) of sheep and in 2.1% (1/47) of beef cattle sold at markets. Canine trichinellosis was recorded in 13 Provinces, Autonomous Regions or Municipalities (P/A/M) and the average prevalence of the infection in dogs slaughtered in abattoirs was 16.2% (5654/34,983) ranging from 1.2% to 44.8%, with the highest prevalence located in northeast China. The prevalence in dog meat sold at markets was 3.5% (988/27,898) in 5 P/A. Feline Trichinella infection was reported in 10 P/A/M. The prevalence of Trichinella infection in rats varied from 1.1% (51/459) to 15.1% (50/332). Trichinella larvae were detected in 1.5% (9/587) of house rats (Rattus norvegicus) as well as in 0.8% (3/369) of wild rats (Apodemus chevrieri), and the infection was recorded also in other wildlife (foxes, bears, wild boar, weasels, raccoon dogs, muntjak and bamboo rats). Trichinella larvae were detected in 2.6% (4/156) of weasels (Mustela sibirica), 1.5% (2/135) of shrews (Tupaia belangeri) and 7.7% (1/13) of moles (Parascapter leucurus). All Trichinella isolates from domestic pigs were identified as T. spiralis. Some Trichinella isolates from dogs in north-eastern China were identified as T. nativa, which has muscle larvae that are highly resistant to freezing. Twenty-seven outbreaks of human trichinellosis associated with mutton, dog and game meat occurred in China between 1964 and 2004, but the quarantine of Trichinella larvae in such meat is not mandatory in China at present.     

The epidemiology of cattle abortion in Algeria

Tropical Animal Health and Production - In Algeria, the epidemiology of cattle abortions is not well understood. Therefore, the present study aims to estimate the prevalence of abortion in 75...     

The epidemiology of bovine dermatophilosis in Zambia

Bovine dermatophilosis (Senkobo disease) has been reported annually in Zambia for many years. However, its epidemiology under Zambian conditions had never been adequately studied. Officially the disease has never been recognized as being of any economic consequence.A field study was designed and conducted from August to December 1986, to provide estimates of epidemiological statistics and other factors for the period January 1985 to December 1986 in four districts. These districts supported approximately 28% of the national cattle herd. The study was conducted in communally grazed herds as the disease was reportedly of little significance in commercial herds. A total of 365 herds containing 22 344 head of cattle were inspected and the owners interviewed; 286 herds (78.4%) and 1114 cattle (5.0%) were found to be affected. Rainy weather, vegetation type such as grass savannah, woodland savannah and thorny bush, ticks and biting flies were indicated as important factors in the appearance and course of dermatophilosis in Zambia.     

The epidemiology of bovine trypanosomiasis in Colombia

Summary A review is given of the present knowledge of the epidemiology of bovine trypanosomiasis in Colombia. Search of the literature, discussions with veterinarians, and original observations have given information on the distribution and prevalence of the pathogenicTrypanosoma vivax and non-pathogenicT. theileri-like organisms.T. evansi infections of cattle may exist but were not detected. Improved methods of diagnosis forT. vivax are required to elucidate problems of: differentiating clinically similar diseases; the susceptibility of cattle relative to age; transmission; wild animal reservoirs, and economic importance. The indirect fluorescent antibody test is an important technique to this end.

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Sumario Se hace una revisión del conocimiento actual de la epidemiología de la tripa nosomiasis bovina en la república de Colombia. La revisión de literatura, de talladas discusiones con médicos Veterinariosy observaciones personales han proporcionado información sobre la distribución y prevalencia delT. vivax (uno de los tripanosomas patógenos) y de los tripanosomas semejantes alT. theileri (un tripanosoma no patógeno). ElT. evansi es posible que exista en los vacunos pero no fué detectado. Se requieren mejores métodos de diagnóstico paraT. vivax con el objeto de aclarar problemas tales como: diferenciación clínica de enfermedades simila res; la susceptibilidad de los bovinos según su edad; métodos de transmisión; el papel de los animales salvajes como reservorios y la importacia económica de las tripanosomiasis. Para conseguir estos objectivos se requiere el uso de la técnica de la fluorescencia indirecta de anticuerpos.

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Résumé Il s’agit d’une revue des connaissances actuelles sur l’épidémiologie de la trypanosomose bovine en Colombie. Des recherches bibliographiques, des entretiens avec les vétérinaires et des observations originales ont permis d’acquérir des renseignements sur la distribution et l’importance deT. vivax pathogène et d’un trypanosome non pathogène ressemblant àT. theileri. Les infections du bétail àT. evansi peuvent exister, mais n’ont pas été décelées. Des méthodes améliorées de diagnostic sont nécessaires pourT. vivax afin d’élucider certains problèmes: diagnostic différentiel avec des maladies cliniquement semblables, sensibilité du bétail en fonction de son age, transmission, animaux sauvages ‘réservoirs’, importance économique. On suggère que la méthode d’immunofluorescence indirecte pourrait être très utile à ces fins.

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E. A. Wells 10th April, 1967–12th July, 1967, and 4th Sept., 1969–13th Dec., 1969; W. A. Page, 7th Sept., 1969–13th Dec., 1969.     

The epidemiology of fasciolosis in Papua New Guinea

Fasciola hepatica metacercariae were present on pasture throughout the year at the trial site. The highest infection rate in trial sheep occurred in the first year after the beginning of the wet season, in December/January, when contamination of the pasture was maintained by other sheep. Variation in rates of infection in consecutive years was linked to differences in grazing pressure and to a change from sheep to cattle as accompanying grazing stock. A minimum precipitation of 125 mm over 4 consecutive weeks appears to be necessary for infected snails to move from their normal habitats and to contaminate wet pasture with cercariae. Infection of sheep can occur during a dry season if pasture has permanent seepage sites or swampy areas where infected snails can remain active and continue to liberate cercariae.     

The epidemiology of canine Babesia infections in Zambia

This study of 1196 dogs over a period of 18 months determined the seasonal infection patterns of canine babesiosis in Lusaka, the capital city of Zambia. The work also describes a retrospective study of the prevalence of canine babesiosis in laboratory clinical blood samples submitted to the University of Zambia, School of Veterinary Medicine for routine haematological examination from the year 1994 to 2009. A cross-sectional study was also performed to determine the levels of Babesia in a low-income society (during the dry season and the wet season of the year), where 361 samples were collected from dogs presented for mass rabies vaccination campaigns. Morphology of the Babesia indicated that all were of the large-sized Babesia canis infection. Babesia-positive dogs had significantly higher rectal temperatures than negative ones, and dogs younger than 1 year were more likely to be Babesia positive followed by those between 2 and 5 years old. Seasonal trends indicate two peaks, one in the rainy season (November-March) and another in the cold dry season (June/July). Monthly prevalence rates of Babesia ranged from 0% to 2.4% in natural populations and from 0% to 28.6% in laboratory specimens. This study shows that Zambia has lower Babesia prevalence than reported in other African countries.