Emergency response planning for anthrax outbreaks in bison herds of northern Canada: a balance between policy and science

Anthrax outbreaks in northern Canada have implications for ongoing recovery efforts for the threatened wood bison and may pose a health risk to humans, other wildlife, and domestic livestock. RWED and WBNP maintain Anthrax Emergency Response Plans (AERPs) for their respective jurisdictions. An AERP is a pre-planned logistical framework for responding effectively and rapidly to an outbreak so as to minimize spread of the disease, reduce environmental load of spores available for future outbreaks, and minimize risk to public health. In this paper, we describe the main components of an AERP and outline areas for future research.

Anthrax and wildlife

Although livestock anthrax is declining in many parts of the world, with an increasing number of countries probably truly free of the disease, anthrax remains enzootic in many national parks and even in some game ranching areas. These infected areas can present a persistent risk to surrounding livestock, which may otherwise be free of the disease, as well as a public health risk. The authors use as examples the national parks in southern Africa, the Wood Buffalo National Park in northern Alberta, Canada, and the deer ranching counties in south-west Texas, United States of America, to present the range of problems, epidemiology, and control procedures. While many advances have been achieved in the understanding of this disease, research is required into the genotypic grouping of anthrax isolates, improved field diagnostic techniques, and oral vaccines, as well as to provide a better understanding of spore survival in soil and the ecology of the disease under natural conditions.

Bacillus anthracis diversity in Kruger National Park

The Kruger National Park (KNP), South Africa, has a recorded history of periodic anthrax epidemics causing widespread disease among wild animals. Bacillus anthracis is the causative agent of anthrax, a disease primarily affecting ungulate herbivores. Worldwide there is little diversity among B. anthracis isolates, but examination of variable-number tandem repeat (VNTR) loci has identified six major clones, with the most dissimilar types split into the A and B branches. Both the A and B types are found in southern Africa, giving this region the greatest genetic diversity of B. anthracis worldwide. Consequently, southern Africa has been hypothesized to be the geographic origin of B. anthracis. In this study, we identify the genotypic types of 98 KNP B. anthracis isolates using multiple-locus VNTR analysis. Two major types are evident, the A branch and the B branch. The spatial and temporal distribution of the different genotypes indicates that anthrax epidemic foci are independent, though correlated through environmental cues. Kruger B isolates were found on significantly higher-calcium and higher-pH soils than were Kruger type A. This relationship between genotype and soil chemistry may be due to adaptive differences among divergent anthrax strains. While this association may be simply fortuitous, adaptation of A types to diverse environmental conditions is consistent with their greater geographic dispersal and genetic dissimilarity.

Multiple-locus variable-number tandem repeat analysis reveals genetic relationships within Bacillus anthracis

Bacillus anthracis is one of the most genetically homogeneous pathogens described, making strain discrimination particularly difficult. In this paper, we present a novel molecular typing system based on rapidly evolving variable-number tandem repeat (VNTR) loci. Multiple-locus VNTR analysis (MLVA) uses the combined power of multiple alleles at several marker loci. In our system, fluorescently labeled PCR primers are used to produce PCR amplification products from eight VNTR regions in the B. anthracis genome. These are detected and their sizes are determined using an ABI377 automated DNA sequencer. Five of these eight loci were discovered by sequence characterization of molecular markers (vrrC(1), vrrC(2), vrrB(1), vrrB(2), and CG3), two were discovered by searching complete plasmid nucleotide sequences (pXO1-aat and pXO2-at), and one was known previously (vrrA). MLVA characterization of 426 B. anthracis isolates identified 89 distinct genotypes. VNTR markers frequently identified multiple alleles (from two to nine), with Nei's diversity values between 0.3 and 0.8. Unweighted pair-group method arithmetic average cluster analysis identified six genetically distinct groups that appear to be derived from clones. Some of these clones show worldwide distribution, while others are restricted to particular geographic regions. Human commerce doubtlessly has contributed to the dispersal of particular clones in ancient and modern times.

Molecular diversity in Bacillus anthracis

Molecular typing of Bacillus anthracis has been extremely difficult due to the lack of polymorphic DNA markers. We have identified nine novel variable number tandemly repeated loci from previously known amplified fragment length polymorphism markers or from the DNA sequence. In combination with the previously known vrrA locus, these markers provide discrimination power to genetically characterize B. anthracis isolates. The variable number tandem repeat (VNTR) loci are found in both gene coding (genic) and non-coding (non-genic) regions. The genic differences are 'in frame' and result in additions or deletion of amino acids to the predicted proteins. Due the rarity of molecular differences, the VNTR changes represent a significant portion of the genetic variation found within B. anthracis. This variation could represent an important adaptive mechanism. Marker similarity and differences among diverse isolates have identified seven major diversity groups that may represent the only world-wide B. anthracis clones. The lineages reconstructed using these data may reflect the dispersal and evolution of this pathogen.

World Health Organization activities on anthrax surveillance and control

The achievements of a World Health Organization Anthrax Working Group, established in 1990, have been the production of two editions of guidelines on anthrax surveillance and control and the formulation of templates to assist countries in the construction of their surveillance and control programmes. The latter was made possible by the active participation of the Department of Animal Production and Health, Ministry of Agriculture, Food and Fisheries, Zambia and the Livestock Development Programme, Mongu, Western Province, Zambia in a model country programme designed by the Working Group for the purpose. This paper elaborates on these achievements, particularly the lessons learned from the experience of Western Province, Zambia.

Meso-scale ecology of anthrax in southern Africa: a pilot study of diversity and clustering

It has only recently been possible to detect sufficient genetic diversity among anthrax isolates to allow genotype grouping (Keim et al. 1997). Early results of such grouping suggest that the southern African subcontinent may be the geographical origin of Bacillus anthracis. This report describes a pilot investigation of the genetic diversity of a study group of isolates from the Kruger National Park, South Africa, and efforts to detect spatio-temporal clustering within the study group. This study has also served as further validation for the newly developed Multi-Locus VNTR Analysis (MLVA), designed to simplify genotyping of B. anthracis isolates. The results reveal a diverse range of genotypes within the park allied with three genotype reference groups, and show that the MLVA procedure is robust for rapid analysis of B. anthracis genotypes. We also observed multiple genotype groups within epidemics and between geographically and temporally close epidemic episodes. This is in contrast to earlier characterizations of anthrax epidemics. The result of a Mantel test for time-space clustering indicates clustering of the anthrax isolates selected for the study.

Evaluation of alternative strategies to prevent Newcastle disease in Cambodia

Velogenic viscerotropic Newcastle disease (vvNCD), which is endemic in Cambodia, can be prevented in theory by a combination of biosecurity and immunization of broiler flocks. The relative contribution of appropriate biosecurity and effective vaccination was quantified at the farm level, applying realistic projections for capital investment, fixed and variable production costs and losses following infection. Non-protected broiler flocks generate a loss when the probability of vvNCD infection exceeds 0.4. Applying both biosecurity and effective vaccination would sustain profitability up to a probability of exposure of 1.0. The benefit to cost ratios for alternative strategies were evaluated for a range of probabilities of exposure to vvNCD extending from 0.1 to 1.0. The benefit-to-cost ratio for biosecurity exceeded unity at a risk of exposure exceeding 0.1, and 0.2 for vaccination and the combination of vaccination and biosecurity respectively. A sensitivity analysis demonstrated that the efficiency of protection, feed cost, and financial consequences of infection markedly affected the projected benefit-to-cost ratios associated with alternative methods of prevention.

PCR analysis of tissue samples from the 1979 Sverdlovsk anthrax victims: the presence of multiple Bacillus anthracis strains in different victims

An outbreak of human anthrax occurred in Sverdlovsk, Union of Soviet Socialists Republic (now Ekaterinburg, Russia) in April 1979. Officials attributed this to consumption of contaminated meat, but Western governments believed it resulted from inhalation of spores accidentally released from a nearby military research facility. Tissue samples from 11 victims were obtained and methods of efficiently extracting high-quality total DNA from these samples were developed. Extracted DNA was analyzed by using PCR to determine whether it contained Bacillus anthracis-specific sequences. Double PCR using "nested primers" increased sensitivity of the assay significantly. Tissue samples from 11 persons who died during the epidemic were examined. Results demonstrated that the entire complement of B. anthracis toxin and capsular antigen genes required for pathogenicity were present in tissues from each of these victims. Tissue from a vaccination site contained primarily nucleic acids from a live vaccine, although traces of genes from the infecting organisms were also present. PCR analysis using primers that detect the vrrA gene variable region on the B. anthracis chromosome demonstrated that at least four of the five known strain categories defined by this region were present in the tissue samples. Only one category is found in a single B. anthracis strain.

The estimated long-term impact of tsetse control on the size of the population of cattle in the Didessa Valley, western Ethiopia

The long-term impact of tsetse control on cattle population size in the Didessa Valley, western Ethiopia, was analysed using an age-structured population model. A prior analytical assessment revealed that the risk of cattle dying in the tsetse-unprotected villages ranged from 4 to 9 times higher than in the tsetse-protected village. Model results show that during a period of 10 years the cattle population in the tsetse-protected village of Meti is likely to increase from 167 to 583 animals, while that in the adjacent tsetse-unprotected village of Gale remains almost constant. Model simulations also predict that improving the survival rate of calves in the tsetse-unprotected villages of Taikiltu and Temoloko (which presently have calf mortality rates of up to 35% would bring a substantial increase in their cattle population.

National survey of clinical and subclinical mastitis in Jamaican dairy herds, 1985-1986

Between April 1985 and August 1986, 89 Jamaican dairy herds with 10 or more cows were visited, 1,645 lactating cows were examined using the CMT test and 254 composite milk samples collected for bacteriological examination. Widespread management faults were noted, especially of milking machine usage and maintenance and the abuse of antibiotics. Fifty-six per cent of all quarters were found to have CMT scores of one or higher, 0.8% showed clinical mastitis and 3.2% were blind. The most common bacterial pathogen Staphylococcus aureus, was recovered from 31% of sampled cows. The resultant milk loss from clinical and subclinical mastitis was estimated to be 20% of the potential national production.

Serological survey for leptospiral antibodies in goats in St Elizabeth Parish, Jamaica, 1985-1986

A serological survey of goats in St Elizabeth Parish, Jamaica, comprising the breeding herd at the Agricultural Development Corporation (ADC) facility at Hounslow, five commercial herds and 21 family herds was carried out in 1985-1986. The Leptospira microscopic agglutination test indicated that one or more serovars in the Canicola serogroup were the most prevalent. Repeated samplings of goats at ADC, Hounslow demonstrated an increase in portlandvere and canicola seropositive animals following the onset of warmer weather and of icterohaemorrhagiae seropositive animals following the autumn rains and cooler weather. Apart from a cluster of family goats seropositive to pomona there was no geographical separation of reactors to the other serovars tested in the parish.

The financial and production impacts of bovine dermatophilosis in Zambia

During October to December 1986, 365 traditional cattle herds in four provinces in Zambia were inspected and the owners interviewed. Information was collected on the treatment, management and disposal of cases of bovine dermatophilosis and on the effects of this disease on productivity for 1985. The contemporary financial cost per case of treatment and/or premature disposal, slaughter or death to the owners was K. 202 (US$91). The cost due to draft oxen being affected was estimated at K. 428 (US$193) per affected ox. The cost of reduced milk production, replacing affected cows and calf deaths, directly or indirectly from bovine dermatophilosis, was estimated at K. 132 (US$78) per affected milking cow. The total annual national cost of bovine dermatophilosis in 1985 was conservatively estimated to be some K. 6.9 million, (US$3 million). There were indications that the true financial cost in 1985 may have been up to 1.8 times the estimated cost.

Seroepidemiology of Anaplasma marginale in white-tailed deer (Odocoileus virginianus) from Louisiana

Antibodies to Anaplasma marginale were detected by the indirect fluorescent antibody test (IFA) in six of 331 (2%) serum samples of white-tailed deer (Odocoileus virginianus) from Louisiana. None of the serum samples were positive using the A. marginale modified rapid card agglutination test. Of the six IFA positive sera retested by the complement fixation test four sera gave anticomplementary and two gave seropositive reactions. The low A. marginale reactor rate in this white-tailed deer population was probably a reflection of the lack of cohabitation between cattle and deer and the fact that the primary arthropod vectors in Louisiana are tabanids. The validity of the indirect fluorescent antibody test for A. marginale antibodies in white-tailed deer should be evaluated.

Incidence of clinical anaplasmosis in cattle in the Red River Plains and south-east areas of Louisiana

Incidence rates for clinical anaplasmosis were estimated for dairy and beef cattle in the Red River Plains and South-east areas of Louisiana. Annual incidence rates of 0.33% and 0.21% were found in dairy cows for 1983 and 1984 while a 31.0% rate was found in beef cows for 1983. The rates were based on postal surveys of dairy and beef cattle producers. A survey of veterinary practices and a follow-up of respondents to the surveys provided a description of 256 cases of anaplasmosis. Eighty-one percent of the clinical cases occurred in cattle aged 4-6 years and 88% of the cases occurred during the months of July-September.

The effect of management and ecological factors on the epidemiology of anaplasmosis in the Red River Plains and south-east areas of Louisiana

The relationship between clinical anaplasmosis and other disease morbidity, nutritional supplementation, vaccinations, external and internal parasite control, tetracycline supplementation, reproductive management and use of veterinary services was assessed in 320 beef cow-calf herds in the Red River Plains and south-east areas of Louisiana. Data were collected both by mailed questionnaires and by interviews with owners who reported the presence or absence of clinical anaplasmosis. A relationship was found between other disease conditions and anaplasmosis, suggesting disease as a stressor in Anaplasmosis marginale carrier cattle. The herd location of A. marginale seropositive animals and clinical cases of anaplasmosis were related to areas of bottomland hardwood vegetation in which tabanid flies were abundant. This relationship with vegetation was tested by mapping the location of 209 beef and dairy herds which had been serologically tested for anaplasmosis and 256 cases of clinical anaplasmosis in 113 beef and dairy herds.

Seroprevalence of anaplasmosis in the Red River Plains and south-east areas of Louisiana

The indirect fluorescent antibody test was used to detect antibodies to Anaplasma marginale in serum samples collected from cattle in the Red River Plains and South-east areas of Louisiana. Convenience sampling of herd clusters was used. A reactor rate of 7.8% was found in 11,085 samples. Beef cattle had a 11.2% reactor rate compared with 3.8% for dairy cattle. The Angus and Angus cross-breed group had the highest reactor rate.

The cost of anaplasmosis in the Red River Plains and south-east areas of Louisiana

Losses from morbidity and mortality due to anaplasmosis were assessed in beef and dairy cattle of the Red River Plains and south-east areas of Louisiana. The cost of treatment and prevention of anaplasmosis and losses in milk production and those due to deaths or culling were valued at $0.5 million for the year 1983 in these two areas. The cost of prevention included the use of tetracyclines in feed and salt-mineral supplements, injectable tetracycline, vaccination and an estimated 10% of the cost of insecticidal ear tags, sprays, pour-on applications and dust bags. The remainder of these costs and the total cost of vector control in dairy cattle was attributed to the control of fly annoyance. Treatment costs included veterinary fees and the owner's treatment costs, including labour costs.

Surveillance for naturally acquired leprosy in a nine-banded armadillo population

Samples from 77 nine-banded armadillos (Dasypus novemcinctus) inhabiting a 16.7 km portion of the East Atchafalaya River Levee, Point Coupee Parish, Louisiana, were serologically tested and/or histopathologically examined for evidence of naturally acquired leprosy. Five of 67 (7.5%) armadillos tested sero-positive with ELISA test for IGM class antibodies to the phenolic-glycolipid-1 antigen of Mycobacterium leprae. One of 74 (1.3%) was histopathologically positive as determined by presence of acid-fast bacteria in nerves.

Prevalence of Toxoplasma gondii antibodies in southern Louisiana swine in 1980 and 1981

Sera from 1,219 pigs slaughtered in southern Louisiana in 1980 and 1981 were tested, using the indirect hemagglutination test and microtitration system, for Toxoplasma gondii antibodies; 19.19% had titers of greater than or equal to 1:64. Pigs slaughtered in the colder months, November to March, had significantly higher seroprevalences than did pigs slaughtered in the warmer months. Examination of blood samples from 236 sows and gilts on 52 farms revealed a seroprevalence of 24.6%.

Evaluation of the origin of Mycobacterium leprae infections in the wild armadillo, Dasypus novemcinctus

An enzyme-linked immunosorbent assay (ELISA) using the phenolic glycolipid-1 (PGL-1) antigen of Mycobacterium leprae and cross-reactive antisera specific for human IgM was developed to detect IgM antibodies to M. leprae in the nine-banded armadillo (Dasypus novemcinctus). Statistical definitions for positive and negative interpretations in the ELISA were developed by screening animals recently captured and experimentally inoculated with M. leprae. The ELISA was shown to have high sensitivity and specificity. Modern day armadillos of central Louisiana were observed to have a PGL-1 antibody prevalence rate as high as 20%, and a clinical disease rate as high as 5%. A retrospective serological survey of 182 armadillos taken in the years 1960-1964 and predating the use of armadillos in leprosy research was used to evaluate the 1968 environmental contamination hypothesis for the origin of M. leprae infections in the wild armadillo. Antibodies to the apparently species-specific PGL-1 antigen were detected in 17 of the samples taken in 1960-1964. Absorption with whole M. leprae, M. intracellulare, M. terrae, M. rhodesiae, M. scrofulaceum, M. diernhoferi, M. kansasii, M. phlei, M. avium, BCG, and 2 new armadillo-derived mycobacterial species showed these antibody reactions to be specific for PGL-1. Apparently, M. leprae was enzootic in armadillos as early as 1961, and original infection of these animals could not have occurred in 1968.

Prevalence of toxoplasma antibodies in Southern Louisiana swine

Sera from 1,219 pigs slaughtered in Acadian Louisiana in 1980 and 1981 were tested using the indirect hemagglutination test and microtiter system for toxoplasma antibodies and 19.2% had titers of 1:64 or higher. Pigs slaughtered in the colder months, November to March, had significantly higher seroprevalences than pigs slaughtered in the warmer months. 24.6% of 236 farm bled sows and gilts had similarly high titers.

Diskospondylitis in a kennel of dogs: clinicopathologic findings

Selected aspects pertaining to the cause and pathogenesis of diskospondylitis were investigated in a kennel of 45 Airedale Terriers. Diskospondylitis was detected via spinal radiography in 17 male and 14 female dogs. Bacteria isolated from the coat, vagina, and urine of affected Airedales were not statistically different from those isolated from clinically normal Airedales. Serologic evidence of Brucella canis infection was not detected. There was no difference in response to thyrotropin stimulation tests between affected and clinically normal dogs. Necropsy findings in affected dogs included hypercellular renal glomeruli and pulmonary arterial thrombi.

Prevalence of trichinosis in southern Louisiana swine

After an outbreak of human trichinosis in Louisiana involving 45 cases and 1 death in 1979 and 1980, a survey of pigs killed in 21 selected small slaughterhouses in southwestern Louisiana was conducted from November 1980 to September 1981. The sera from 1,225 pigs were examined for trichinella antibodies using an enzyme-linked immunosorbent assay (ELISA); 1,223 diaphragms were subjected to peptic digestion and examined for the presence of Trichinella spiralis larvae. One diaphragm (0.08%) was found to contain T spiralis (26 larvae/g of muscle) and 4 of the slaughterhouse sera were positive (0.33% seroprevalence). Pigs in 52 herds throughout the state were also tested for ELISA antibodies. The ELISA-positive pigs were not found among the 267 pigs tested from the 52 herds.

Serological study of the incidence and prevalence of antibodies to bovine leukemia virus in aged sera

Ninety-seven sera collected from 21 animals that had been repeatedly sampled more than 17 years before and stored at -18 degrees C were tested for bovine leukemia virus antibodies using the agar gel immunodiffusion test. The prevalences for the different ages matched current prevalences in the same herd. The consistency of these results over a prolonged period suggests the validity of long-term retrospective seroepidemiological studies of this disease. Because the original titers could not be determined and some indications of a possible loss of activity, the results must be interpreted with a measure of caution.

Leptospiral and brucellar titers in frozen bovine sera after 20 years of storage

Generally good agreement was obtained between the rankings of sera titers when originally tested (T1), and those of the same sera 20 years later (T2). At the later time, the majority of samples (88%) were in, or within 1 dilution factor of their classification at T1. Test results for Brucella abortus and Leptospira interrogans var pomona antibodies demonstrated that original titers, in the upper-lower limits of 20 to 50, had decreased over a wide range (20% to 90%), and the later tests show that the greater the original titer, the greater the proportional decrease. Thus, titers of 20,000 at T1 had decreased by 49% to 99% and those of 200,000, by 95% to 99.8%. Variations in T2 test results were noted between some samples which had given identical results at T1. A decrease in titer over time has been demonstrated. An estimate of the expected half-lives of sera of differing initial Leptospira antibody titers is that for each unit increase in log10 of the initial titer, the half-life is reduced by about 50%. The heterogeneity of the immune response is postulated as the reason for this variation.

Epidemiological studies on the 1967-1968 foot-and-mouth disease epidemic: the reporting of suspected disease

From an analysis of the telephone reports in ten FMD Control Centres in the West Midlands, the veterinary officers' reports on each outbreak, the farm patrol reports and the daily number of outbreaks announced on the 17.50 h B.B.C. T.V. News, it would appear that the reporting of suspected outbreaks was indirectly related to the local disease activity. Private veterinary practitioners reported older cases of FMD at the beginning and end of the epidemic than in the middle.

Studies on the 1967--68 foot and mouth disease epidemic: incubation period and herd serial interval

The incubation period during this epidemic was studied using both a spectral analysis-cum-filtering method and analysis of case histories. Using spectral analysis, the modal herd serial interval was estimated to be 8--10 days based on the record of the daily number of outbreaks and an adjusted cattler series. The case histories tended to confirm these estimates but indicated that the serial interval varied considerably between species. The filtering method revealed that the herd serial interval apparently changed during the epidemic. For the first 4 weeks the interval was 8 days, while in the latter stages it was about 2 weeks.

A simulation spatial model of the spread of foot-and-mouth disease through the primary movement of milk

A computer model was constructed to mimic the 1967-8 foot-and-mouth epizootic in Shropshire and Cheshire, but the daily spatial distribution of outbreaks was randomized. This pattern of outbreaks was then examined to determine what percentage of outbreaks would fulfil and arbitrary set of criteria for milk-lorry-borne disease, or the primary movement of milk. Some 21% of herds visited subsequent to a 'source farm' were affected, as were 4% of herds visited after any infected herd. The relevance of these results to the true risk of disease through the primary movement of milk off affected farms is discussed.

Rabbit mortality survey

In a survey of mortality in 2224 rabbits of up to 12 weeks of age, drawn from 10 production units, neonatal mortality was important with 111 stillbirths and 175 deaths in the 1st week of life out of a total of 457 deaths in the whole survey. There was a low overall incidence of death from respiratory and enteric disease during the period of study.

Anthrax in England and Wales 1963-1972

The records of confirmed anthrax diagnoses held by the bacteriology department of the Central Veterinary Laboratory, Weybridge, for the years 1963 to 1972 inclusive, were analysed. During this decade, 86 per cent of the 2944 deaths recorded were in cattle and 11 per cent in pigs, correlating significantly with the cattle and pig populations in England and Wales during this period. Also, the country could be separated into high and low prevalence counties for cattle anthrax. Norfolk and Somerset had higher than usual cattle deaths per farm ratios and the reasons for this are explored.

The cost of premature death in young rabbits

The costs of death in a model 100-doe commerical rabbit unit were calculated on the basis of two levels of breeding (7.5 and 10.0 litters per doe per year) and two levels of feeding, (ad lib and controlled). Although the cost of individual deaths from stillbirth and other perinatal and neonatal deaths was half or two-thirds the cost of an individual death later in the rabbit's life, the total cost of these early deaths was three times the total cost of the later deaths. Early death thus plays a major part in the profitability of a commercial rabbitry.

Studies on the 1967-8 foot-and-mouth disease epidemic. The relation of weather to the spread of disease

An analysis of the 1967-8 foot-and-mouth disease epidemic with reference to the initial spread, the origin of outbreaks more than 60 km. from the main epidemic area, the series of outbreaks near Worcester, a specific case history and the daily rate of spread of the epidemic, strongly suggests that the weather played a major part in the spread of disease. The two main factors involved in this type of spread are wind and precipitation. It is noted that after the epidemic had been checked, following anticyclonic weather, the association between the weather and the spread of disease was less apparent.

Epidemiological studies on Salmonella senftenberg. I. Relations between animal foodstuff, animal and human isolations

It was possible to demonstrate from retrospective records that a link existed between contaminated animal feedstuffs, turkeys and an outbreak of Salmonella senftenberg infection at Ryhope Hospital. Possibly infected or contaminated turkeys were supplied to the hospital from two turkey farms in one of which the birds were fed on contaminated white fish meal and the other had had infected birds.

This work was carried out months after the events described and would not have been possible without the help and co-operation of the Public Health Laboratory Service, The Veterinary Field, Investigation and Research Services, Houghton Poultry Research Station, The Medical Officer of Health for Brighton, Dr Rosetta Parker, and the various feed companies involved, who very kindly made their records available to us.

Epidemiological studies on Salmonella senftenberg. II. Infections in farm animals

Between August 1964 and November 1965Salmonella senftenbergwas isolated from poultry, sheep and cattle on eight farms in England and Scotland. From an analysis of the case records its presence would appear to be incidental; but it may contribute to poultry mortality by acting in conjunction with other intercurrent infections or following stressful events such as severe debeaking or cold brooder conditions.

I should like to thank the officers of the veterinary field investigation and research services who made available their records and notes for this work, and who visited the farms and hatcheries, but especially Mr R. Duff, Veterinary Laboratory, Lasswade, for his reports on the turkey poults from farm A; also Dr Betty Hobbs and Mr B. Hanson for their valuable criticisms.

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.