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EDUCATION and TRAINING
B.S. 1976 North Carolina State University, Animal Science
M.S. 1978 The Ohio State University, Dairy Science
Ph.D. 1980 The Ohio State University, Dairy Science
RESEARCH INTERESTS
Mastitis in dairy cows is a complex multifactor disease and is
likely the most costly disease affecting animal agriculture in the
world. Mastitis differs from other animal diseases in that several
diverse bacteria are capable of causing the disease. Control is
extremely difficult due to diverse types and sources of mastitis
pathogens coupled with a poor understanding of bacterial and host
factors associated with the disease process. Mastitis caused by
environmental pathogens such as Streptococcus uberis is particularly
problematic because current methods of control are less effective,
often ineffective, against pathogens that are ubiquitous in the
dairy farm environment. Consequently, mastitis caused by environmental
pathogens remains a serious problem in several herds, and can become
a significant problem in dairies that have controlled the more common
mastitis pathogens. Research conducted by Dr. Oliver has focused
extensively on mastitis in dairy cows, particularly mastitis caused
by environmental pathogens such as Streptococcus uberis.
Objectives of Dr. Oliver's research are to: 1) characterize factors
which affect resistance of the udder to mastitis, 2) characterize
factors and mechanisms which permit mastitis pathogens to invade
the udder and produce mastitis, 3) develop and evaluate techniques
for the prevention and control of mastitis in dairy cows, and 4)
characterize dairy food safety issues relevant to mastitis.
RESEARCH ON HEIFER MASTITIS: Dr. Oliver demonstrated that
mastitis in pregnant heifers was much higher than previously thought.
Many of these infections can persist for long periods, are associated
with elevated somatic cell counts, and likely impair mammary development
during gestation and affect milk production after calving. Collectively,
results of studies on prevention and control of heifer mastitis
by Dr. Oliver demonstrated that prepartum intramammary antibiotic
infusion of heifer mammary glands a few weeks before calving is
an effective procedure for eliminating many infections in heifers
during late gestation and for reducing the prevalence of mastitis
in heifers both during early lactation and throughout lactation.
Prepartum antibiotic-treated heifers produced significantly more
milk and had significantly lower somatic cell count scores than
untreated control heifers. Prepartum antibiotic treatment to reduce
mastitis in heifers during early lactation was economically beneficial.
Prepartum antibiotic-treated heifers produced 531 kg more milk than
heifers in the untreated control group. Multiplying this increase
by a milk price of $0.408/kg yielded a $216.24 per-heifer increase
in gross revenue. Subtracting the cost of treatment from gross revenue
(including the cost of testing for antibiotic residues), the net
revenue from the actual production increase amounted to $200.64
per heifer.
 IDENTIFICATION
AND CHARACTERIZATION OF STREPTOCOCCAL VIRULENCE FACTORS: RELATIONSHIP
WITH IMMUNITY TO MASITITS IN DAIRY COWS:Relationship with Immunity
to Mastitis in Dairy Cows: Another very active area of research
in Dr. Oliver's laboratory is identification and characterization
of streptococcal virulence factors and their relationship with immunity
to mastitis. Nonantibiotic approaches for the prevention and control
of environmental mastitis in dairy cows is an appealing concept.
Studies aimed at development of new vaccines against mastitis pathogens
that are refractory to current methods of mastitis control are likely
to have huge payoffs in the future as use of antibiotics in the
dairy industry come under greater scrutiny by federal regulatory
agencies. Initial studies have focused primarily on Strep. uberis.
In many dairy herds, Strep. uberis is responsible for a high
proportion of clinical and subclinical mastitis in lactating cows,
and is the predominate organism isolated from mammary glands during
the nonlactating period. Strategies for controlling Strep. uberis
mastitis are poorly defined and currently inadequate. Objectives
focus on: 1) genotypic characterization of Strep. uberis;
2) phenotypic characterization of Strep. uberis with particular
reference to bacterial cell surface components and factors involved
in bacterial adherence and invasion; 3) development of a Strep.
uberis experimental infection model to characterize the infection
process, and to facilitate evaluation of new control strategies;
and 4) evaluation of the immune response and efficacy of experimental
vaccines for the prevention of Strep. uberis mastitis following
immunization of dairy cows with novel streptococcal antigens. Dr.
Oliver's research group has identified several potential Strep.
uberis virulence factors. These include: hyaluronic acid capsule
surrounding the bacterium; binding to extracellular matrix proteins
such as laminin, collagen, and fibronectin; and bacterial synthesis
and secretion of collagen-binding protein, lactoferrin-binding protein
and M-like protein.
DNA FINGERPRINTING FOR RAPID & ACCURATE DETECTION OF PATHOGENS:
Dr. Oliver's laboratory developed DNA fingerprinting techniques
for identification of several mastitis pathogens including Streptococcus,
Enterococcus, and Staphylococcus species. These procedures
have been used to separate new from persistent intramammary infections
by subtyping pathogens. The same subtype of Strep. uberis or
Strep. dysgalactiae was detected from some mammary glands from
one lactation to the next. DNA fingerprinting procedures developed
in Dr. Oliver's laboratory have also been used as a tool to establish
the role of horn flies in the transmission of Staph. aureus
mastitis in heifers. A Staph. aureus strain with a characteristic
DNA fingerprint pattern was used as a marker strain to determine
if horn flies served as a vector in the transmission of Staph.
aureus mastitis in heifers. When Staph. aureus colonized
horn flies were allowed to feed on teats of uninfected dairy heifers,
intramammary infection with the same Staph. aureus DNA fingerprint
subtype resulted. This indicates that horn flies can transmit Staph.
aureus to heifer teats if a sufficient source of organisms is
present.
DNA fingerprinting techniques developed in Dr. Oliver's laboratory
have also been useful in antimicrobial drug and vaccine efficacy
studies when attempting to delineate new and persistent intramammary
infections. DNA fingerprinting procedures are also being used as
epidemiological tools to determine important on-farm sources of
mastitis pathogens and foodborne pathogens. A grant proposal funded
by the National Pork Board resulted in development of DNA-based
methods for rapid and accurate detection of Salmonella cholerasuis
and Salmonella typhimurium. Molecular profiles of foodborne
pathogens are being evaluated in a study funded by the Food and
Drug Administration to define their distribution within and among
livestock production areas and to determine the environmental sources
of specific subtypes in different geographic regions. This information
will also be useful to track movement of specific subtypes from
one geographical production region to another. The relatedness of
foodborne pathogens isolated from dairy farms can be compared with
existing national databases on human pathogens isolated from cases
of foodborne illness or foodborne disease outbreaks.
INTERACTION OF MASTITIS & REPRODUCTIVE PREFORMANCE:
Even cows from well-managed dairy herds utilizing the most recent
and most effective mastitis control measures experience mastitis,
especially during the 1st 90 days of lactation. Collaborative research
with Dr. F. Neal Schrick of the Department of Animal Science at
The University of Tennessee has shown that mastitis significantly
impairs reproductive performance of dairy cows. Reproductive efficiency
is of great concern to dairy producers because reduced reproductive
performance is associated with a great monetary loss. These losses
are in addition to costs associated with mastitis such as decreased
milk production, altered milk composition, treatment costs, discarded
milk, increased involuntary culling rate, etc.
We recently reported that Jersey cows with clinical and/or subclinical
mastitis during early lactation exhibited a prolonged period until
1st service opportunity than cows with no clinical mastitis. Additionally,
an increased number of days open and services/conception were observed
in cows with clinical or subclinical mastitis between 1st service
and establishment of pregnancy compared to cows not experiencing
clinical mastitis or cows with clinical mastitis either before 1st
service or after pregnancy was confirmed. We found no differences
between effects of mastitis due to contagious or environmental pathogens
on either days to 1st service, days open, or services/conception.
Results suggest that clinical and subclinical mastitis during early
lactation can have a profound effect on reproductive performance
of dairy cows.
PREHARVEST FOOD SAFETY RESEARCH: Reports from the Center
for Disease Control and Prevention, the Food and Drug Administration
and USDA indicate that the risk of foodborne illness has increased
markedly over the last 20 years. Today, nearly a quarter of the
US population is at higher risk for foodborne illness. Costs associated
with foodborne illnesses are exorbitant, estimated to range from
$19 billion to $37 billion annually. The situation becomes even
more problematic because of rapidly changing demographics, with
an increasing number of elderly people and immunocompromised individuals
who are more susceptible to foodborne pathogens. The threats are
numerous and varied such as E. coli O157:H7 in meat and apple
juice; Salmonella in eggs, on vegetables and on poultry;
Vibrio in shellfish; Cyclospora and hepatitis A virus
on fruit; and Cryptosporidium in drinking water. Much has
changed in what we eat and where we eat. Americans are eating a
greater variety of foods, particularly poultry, seafood and fresh
fruit and vegetables. Americans are also eating more of their meals
away from home. This food is purchased and consumed from grocery
stores, restaurants, and in institutional settings such as schools,
hospitals, nursing homes and day care centers. Consequently, as
more people become involved in preparing our meals, the chance for
foodborne illness increases dramatically.
In 1998, Dr. Oliver was instrumental in organizing a food safety
initiative at The University of Tennessee Institute of Agriculture,
which encompasses interdepartmental, multidisciplinary collaborations
among researchers, extension personnel and allied personnel in the
Agricultural Experiment Station, Agricultural Extension Service
and the College of Veterinary Medicine. More recently, Dr. Oliver
was primary author of a proposal to establish a Food Safety Center
of Excellence at The University of Tennessee that was selected to
receive $5 million dollars of University funding. He serves as Co-Director
of The University of Tennessee Food Safety Center of Excellence.
The vision for The UT Food Safety Center of Excellence is
to be the leader in the state, region, nation, and the world in
the development and dissemination of science-based information on
timely and relevant food safety issues and concerns that will minimize
problems associated with foodborne illness; to significantly impact
development of new technologies and economic development; and to
enhance research funding, notoriety and prestige for the university.
Research and development of educational materials by The UT Food
Safety Center of Excellence will be consistent with priority
areas defined by the National Food Safety Initiative. Goals are
to develop and evaluate strategies to destroy or control foodborne
pathogens and reduce the occurrence of foodborne illness; to identify
mechanisms associated with development and transfer of antibiotic
resistance in foodborne pathogens, and devise strategies that limit
occurrence of antibiotic resistant bacteria in foods; to develop
nonantibiotic approaches and other novel strategies, such as identification
of disease resistant animals, for the prevention and control of
diseases of food-producing animals that impact food quantity and
quality; to develop strategies to reduce environmental contamination
with foodborne pathogens during animal production and food processing
through environmental management and risk assessment; and to develop,
communicate and disseminate instructional food safety information
to students (beginning in K-12), consumers, producers and processors
of food products, and the food service industry in Tennessee and
nationally.
The primary goal of pre-harvest food safety research conducted
by Dr. Oliver's laboratory is to provide comprehensive information
on the occurrence of Salmonella, Escherichia coli O157:H7,
Listeria monocytogenes, Campylobacter jejuni, and
other emerging pathogens on dairy farms under varying management
conditions. This information is critical for implementation of on-farm
foodborne pathogen reduction programs. A second objective is characterization
of foodborne pathogens isolated from milk and dairy beef in a study
funded by FDA. Molecular epidemiological patterns and antibiotic
resistance patterns of foodborne pathogens isolated from bulk tank
milk and from cull dairy cows are being delineated. This information
will be useful to track movement of specific subtypes from one geographical
production region to another. The relatedness of foodborne pathogens
isolated from dairy farms can be compared with existing national
databases on human pathogens isolated from cases of foodborne illness
or foodborne disease outbreaks. A third area of interest is development
of accurate and rapid methods for the detection of foodborne pathogens.
A recent grant proposal funded by the National Pork Producers Council
resulted in the development of a PCR-ELISA method for rapid and
accurate detection of Salmonella serogroups A, B, C1, C2
and D with particular emphasis on Salmonella choleraesuis
and Salmonella typhimurium.
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