Outbreaks In Herds Research Articles

Combined parenteral and oral administration of oxytetracycline for control of infectious bovine keratoconjunctivitis

Objective To determine whether combined parenteral and oral administration of oxytetracycline would ameliorate a herd outbreak of infectious bovine keratoconjunctivitis (IBK) and to compare efficacy of this regimen with that of subconjunctival administration of procaine penicillin G. Design Randomized field trial. Animals 119 Hereford calves in a herd undergoing a naturally occurring outbreak of IBK. Procedure Calves were randomly assigned to 1 of the following 3 groups: oxytetracycline treatment, procaine penicillin G treatment, and control. After initial treatment, calves were examined 3 times/wk for 7 weeks. The surface area of all corneal ulcers was measured during each examination. Ocular secretions were collected from all calves at least weekly and were tested for Moraxella bovis. Results Calves treated with oxytetracycline had a lower prevalence of IBK than did calves treated with procaine penicillin G or control calves and required fewer additional treatments than did calves treated with procaine penicillin G. Mean time for healing of corneal ulcers was significantly less for calves that received oxytetracycline or procaine penicillin G than for control calves. Calves treated with oxytetracycline developed fewer corneal ulcers and fewer recurrent ulcers than did calves in the other groups. Moraxella bovis was isolated less often from ocular secretions collected from calves in the oxytetracycline group than from calves in the other groups. Clinical Implications Combined parenteral and oral administration of oxytetracycline appears to be an effective method of reducing severity of a herd outbreak of IBK and may be superior to treatment of affected animals with procaine penicillin G. (J Am Vet Med Assoc 1998; 212:560-563)

An inactivated gE-negative marker vaccine and an experimental gD-subunit vaccine reduce the incidence of bovine herpesvirus 1 infections in the field

An inactivated glycoprotein E-negative vaccine and an experimental glycoprotein D-subunit vaccine against bovine herpesvirus 1 (V1) were examined for their effectiveness in a randomized, double-bline, placebo-controlled field trial comprising 130 dairy farms. The use of these marker vaccines enabled us to monitor the incidence of infections in vaccinated populations. The aims of this trial were to evaluate whether these vaccines: (1) reduce the proportion of outbreaks in dairy herds; and (2) reduced virus transmission within dairy herds and to what extent. Vaccination with either of the two vaccines significantly reduced the proportion of herds wherein an outbreak occurred as well as the virus transmission within herds, as compared to placebo-treated herds. The estimated number of secondary cases caused by one infectious animal, expressed as the reproduction ratio R , was for both vaccines significantly >1. This indicates that when BHV1 is introduced into vaccinated herds, major outbreaks may still occur.

Efficacy of Systemic and Oral Oxytetracycline for Control of a Herd Outbreak of Infectious Bovine Keratoconjunctivitis

The efficacy of a combination of parenterally administered and oral long-acting oxytetracycline formulation was compared to treatment with subconjunctivally administered penicillin in controlling a herd outbreak of infectious bovine keratoconjunctivitis.

Molecular epidemiological studies of Mycobacterium bovis infections in humans and animals in Sweden

Forty-nine isolates of Mycobacterium bovis from humans and animals in Sweden were analyzed by restriction fragment length polymorphism (RFLP) patterns probed by the insertion element IS6110. Most isolates had patterns indicating the presence of only one or two genomic copies of the IS6110 insertion element. This simple type of pattern was found in all human isolates. In contrast, isolates from M. bovis infections in five herds of farmed deer in Sweden showed a specific RFLP pattern with seven bands, indicating seven copies of the IS6110 sequence. In 1958, Sweden was declared free from M. bovis in cattle. However, in 1987, M. bovis was reintroduced with imported farmed deer, and since 1991, 11 outbreaks in deer herds, but not in other livestock or wildlife, have been diagnosed. Continued RFLP studies of the new Swedish M. bovis isolates can reveal possible transmission of this deer strain to other animals or humans.

Epidemiology of Bovine Viral Diarrhea Virus

Prevalence studies around the world show that BVDV is widespread in most cattle raising countries. There are significant differences, however, in prevalence between areas, probably the result of differences in cattle population structure and management practice. Direct contact with PI animals is probably the most important method of transmission of infection; however, field studies have shown that some limited spread of infection also occurs in the absence of PI animals. This may be due to contact with acutely infected animals or contact with other species infected with BVDV. Different ways of indirect transmission such as contaminated needles and equipment have been proven experimentally, and indirect transmission is considered to have some importance. If a PI animal is introduced directly into a dairy herd, most animals will be infected within a few months. On many occasions, however, a herd gets infected by other means than direct introduction of PI animals. In these cases, the infection is often spread to only a few animals after which the infections stops. The infection is then reinforced when PI animals are born. Slow and hence prolonged spread of infection in herds without PI animals also has been described, but the mechanism is not fully understood. Family lines of PI animals delivering PI calves are fairly common and can cause the infection to continue for several years. The clinical manifestations, acute BVDV, reproductive disorders, birth of malformed, weak and undersized calves, unthrifty PI animals, and mucosal disease often appear within certain periods. Large variation, however, can occur between herd outbreaks due to variation in virulence of the BVDV strain, housing of the cattle, and variation in transmission patterns. The extensive transmission of infection from PI animals makes different surveillance methods possible. Thus testing of a screening sample of a few young stock of antibodies and determination of antibody titer in bulk milk will often give good indication of presence of PI animals in herds not using BVDV vaccines. In herds using killed vaccine, determination of antibody titers among few young stock can show the presence of PI animals. The high incidence of infection combined with all the different damages that are seen after BVDV infection cause huge economical losses, which on a national level in the UK and Denmark (i.e., areas with widespread occurrence of infection) has been calculated as between 7 and 27 million pounds (between $11 and $42 million) per million calvings. Epidemiologic studies are important as a basis for selection of control strategy. Because of the variation in epidemiology between geographic areas, evaluation of a control strategy in an area preferentially should be based on epidemiologic studies in the same area.

Eperythrozoon infection in young bulls with scrotal and hindlimb edema, a herd outbreak

Young (9 to 10 mo) Aberdeen-Angus bulls (n = 5) in excellent body condition and pastured with approximately 35 other bulls of similar age on a farm in southeastern Alabama had fever, harsh pulmonary sounds, increased respiratory rate and variable amounts of hindlimb and scrotal edema. Bulls had mild microcytic, normochromic anemia. Numerous eperythrozoon organisms were identified on blood smears. Indirect hemagglutination inhibition test results for Eperythrozoon suis antibodies were negative either because E. suis antigens do not cross react with cattle eperythrozoon organism antibodies or blood was collected before there was sufficient time for seroconversion. Bulls had swelling of the scrotal wall, soft testes, and poor semen quality, characterized by low progressive motility and a high percentage of spermatozoa with primary and secondary abnormalities. Some of these abnormalities may be attributed to the age of the bulls. However, loss of scrotal thermoregulation was a major cause of testicular degeneration leading to poor semen guality. Other bulls in the herd had fever, increased respiratory rate, and swollen hindlimbs or scrotum. Subsequent to administration of oxytetracycline, parasitemia resolved rapidly, and clinical signs gradually abated. Four of five bulls successfully passed breeding soundness examinations six months after initial clinical illness. The remaining bull failed twice due to the presence of testicular inflammation.

Diagnostic value of phage typing, antibiogram typing, and plasmid profiling of Staphylococcus hyicus from piglets with exudative epidermitis.

A total of 989 isolates of S. hyicus were recovered from the skin of 103 piglets (9.6 isolates per piglet) with exudative epidermitis (EE), and phage typed. Phage patterns of 806 typable isolates (81%) could be divided into 44 distinct phage types. From 1 to 6 different phage types were found on individual piglets, with an average of 1.9 phage type per piglet. Antibiogram patterns of 384 isolates from 40 randomly selected piglets with EE showed a mean of 2.3 different antibiograms per investigated piglet, ranging from 1 to 6 antibiograms per piglet. Plasmid profiles of 248 S. hyicus isolates from 25 randomly selected piglets showed an average of 2.8 different plasmid profiles per piglet. Seven EE outbreaks in pig herds vaccinated with autogenous vaccine were investigated. In all these herds, strains recovered from the present outbreak differed by two or more type markers to the strains from the previous outbreak used for production of the autogenous vaccine. This finding suggest, that lack of protection might be due to the presence of other virulent types in the investigated herd than those used for production of autogenous vaccine.

A simple field diagnostic smear test for bovine besnoitiosis

A fast and inexpensive skin biopsy smear was used for confirming suspected clinical cases of bovine besnoitiosis. The technique was based on the demonstration of Besnoitia besnoiti bradyzoites (cystic stages), which appeared stumpy, each organism 6.2 μ by 3.1 μm in size,banana-shaped 7.7 μm by 1.5 μm in affected skin smears. A more rapid non-surgical technique, scleral conjunctival scraping, revealed similar bradyzoites, thus enhancing the diagnostic value of conjuctival cysts in more chronic infections. The technique will aid prompt management decisions to contain suspected outbreaks in herds not routinely served by tissue-processor-equipped diagnostic laboratories.

Corynebacterium pseudotuberculosis associated skin disease of Holstein cattle in the San Joaquin Valley, California

The role of Corynebacterium pseudotuberculosis in diseases of sheep and goats, particularly caseous lymphadenitis, is well recognized. However, there are few reports in the North American literature of Corynebacterium pseudotuberculosis causing diseases of cattle. There is a case report of Corynebacterium pseudotuberculosis associated with otitis media in feedlot cattle but there are no reports of its association with skin disease of cattle. By contrast, the Egyptian literature contains many case reports of an "oedematous skin" disease which occurs primarily in buffalo, but which has also been reported in cattle. Edematous skin disease is associated with C. pseudotuberculosis.
 In this report the clinical findings are described for a herd that was affected by an outbreak of severe skin disease associated with Corynebacterium pseudotuberculosis. Pathology, microbiology and treatment of this condition are discussed. Herd outbreaks of this condition appear to be not uncommon in the San Joaquin Valley based on records of the California Veterinary Diagnostic Laboratory System at Tulare (CVDLS) which record seven additional herd outbreaks since 1987. Herd outbreaks are characterized by the sudden onset of skin lesions in a number of animals. All outbreaks have occurred between October and February. The condition is severe and results in losses due to culling, treatment costs and problems with milking parlor cleanliness and disinfection.

Evaluating Risk Factors in Disease Outbreaks

The investigation of disease outbreaks in herds and flocks includes the gathering of multiple types of discrete data on the characteristics of the disease and the potential risk factors involving agent, host, and environment. Descriptive statistics such as rates, ratios, and proportions offer the investigator tools for counting the disease occurrence, for communicating the results of the investigation to others, and for further analyzing the patterns of disease in order to identify the true risk factors. Because there are several alternative methods for calculating descriptive statistics, specific definitions of each statistic should be followed so that ambiguity and misinformation are avoided. The practitioner must choose one definition and apply it consistently in disease investigations. Consistency allows for comparison of descriptive statistics from one investigation to another, or from one time to another time within the same herd. Analytic statistics allow for a critical evaluation of the data represented in rates, ratios, and proportions. Statistical tests address the all-important question, "Could these observed associations between disease and potential risk factors have occurred by chance alone?" This question must be addressed so that the wisest intervention decisions can be made. The tools described in this article are useful in routine herd health practice situations as well as the investigation of disease outbreaks and impaired productivity. Descriptive statistics provide a system for counting disease so that the practitioner can evaluate progress in the individual herd. The ability of the practitioner to quantify changes in disease occurrence in the herd provides hard evidence for the producer of the impact of herd health approaches.

Serological Characterization of Haemophilus Pleuropneumoniae (Actinobacillus Pleuropneumoniae) Strains and Proposal of a New Serotype: Serotype 9

Ten strains of H. pleuropneumoniae isolated from 10 herd outbreaks of pleuropneumonia were studied by means of the slide agglutination test, the indirect haemaggluitiniation (IHA) test and by gel diffusion. The strains were antigenically homogeneous and serologically distinct from serotypes 1 through 8. It is therefore proposed to refer these strains to a new serotype: serotype 9, with strain CVJ 13261 as the type strain. In addition to the serotype-specific capsular antigens, capsular antigen of serotype 1 (strain 4074) could be demonstrated in the 10 strains by means of gel diffusion analyses. In cross protection studies it was shown that the antigenic determinants shared by serotypes 9 and 1 were unable to yield a sufficient protection against disease. Thus, parenteral immunization with a killed 6-h culture of serotype 9 did not afford an acceptable protection against challenge with serotype 1 since only 3 of the 5 vaccinates were protected. The reverse experiment showed that parenteral immunization with serotype 1 only protected 1 out of 4 vaccinates.

Serological Characterization of 8 Haemophilus Pleuropneumoniae Strains and Proposal of a New Serotype: Serotype 8

Eight strains of Haemophilus pleuropneumoniae isolated from 8 herd outbreaks of pleuropneumonia in pigs were studied by means of the slide agglutination test, the tube agglutination test, the IHA test and by gel diffusion. The 8 strains were antigenically homogeneous and serologically distinct from serotypes 1 through 7. It is therefore proposed to refer these strains to a new serotype: serotype 8, with strain 405 as the type strain. In addition to the serotype-specific capsular antigens, capsular antigen of serotype 3 (strain 1421) and serotype 6 (strain Femo) could be demonstrated in the 8 strains by means of the IHA test and by gel diffusion analyses.

Antigenic variation in FMD virus type Asia 1 strains recovered in India during 1980-1982.

Summary : A total of 43 strains of FMD virus recovered from field outbreaks in different parts of India were processed for subtyping using as the reference strain Asia 1/1 (Pak 1/54) which is the vaccine strain in India. The majority of these strains showed an 'r' value of 0.25 and 0.13 with Asia 1/1 antiserum. The antisera against some of the selected strains were tested in the other direction also and 'r' values less than 0.25 were observed indicating that these strains were of a subtype different from Asia 1/1. Testing of these strains with subtype antiserum Asia 1/2 (Israel 3/63) showed that these strains were homologous to Asia 1/2. Thus the emergence of a new subtype Asia 1/2 (Israel 3/63) as early as 1980 in addition to the prevailing Asia 1/1 subtype was recognized for the first time in India. This could be the reason for the increased incidence of FMD outbreaks in herds which were vaccinated with the vaccine con­ taining Asia 1/1 subtype. The present observations would help in the selection of a suitable vaccine strain for use in vaccine manufacture in India.

Diagnosis and management of bovine chemical toxicoses

Many bovine toxicologic problems considered in the past have been acutely fatal or disabling syndromes. They have been hard to ignore when they occur. Thus acute arsenic poisoning, insecticide induced seizures, and herd outbreaks of nitrate or cyanide poisoning have been well-known examples of problems for veterinary toxicology. Problems like these still exist and may cause devastating losses for individual producers. However, these problems are, for the clinician, generally easily recognized and there are sound recommendations for their control. With the introduction of more complex and numerous chemicals in agriculture and industry as well as changing procedures in livestock production, the classical veterinary poisons are no longer sufficient subject matter for livestock health professionals. Clinical problems induced by newer chemicals may be vague and hard to difine. Death may be less important than an economic effect such as poor performance or increased susceptibility to infectious disease after exposure to toxicants. Presence of illegal residues either from improper use of approved drugs or inadvertent exposure to chemicals continues to be of concern to practitioners, producers and regulators. This paper will deal, not in the entire range of bovine toxicology, but with well- known examples of toxicants which are still real~or potential problems. Some are highly toxic, others are cumulative and cause residues. The reader is urged to consult one or more of the supplemental readings for more complete discussions of classical toxicologic problems.The situations to be discussed are as follows: 1) those problems arising when animals are contacted by chemical products or by-products of industry or commerce 2) toxicologic effects and residues associated with use (misuse) of pesticides or economic poisons, and 3) toxicosis or loss from exposure to metallic poisons.

Etiologic studies of bovine winter dysentery

Study of 20 herd outbreaks of winter dysentery showed that the disease could be transmitted from affected to healthy cattle, but vibrios, infectious bovine rhinotracheitis, bovine viral diarrhoea, parvovirus, enterovirus and other cytopathic bovine viruses did not seem to be involved.

Allergic Pneumonitis in Cattle

During the past year we have investigated herd outbreaks of an unusual respiratory syndrome in two widely separated dairy herds in New York State and one in Canada. The Canadian herd consisted of approximately 70 purebred Holstein milking animals; one of the N.Y. herds was comprised of 40 purebred Guernsey milkers and the other was a “commercial” dairy consisting of approximately 70 head, mostly Holsteins with a few Guernseys and Jerseys. In each herd, the history, signs, progression of the syndrome and subsequent sequellae have been identical.