Brucellosis in the Greater Yellowstone Area (1998) / Chapter Skim
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Part I: The Disease and Transmission
Part I: The Disease and Transmission
Pages 16-41
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From page 16... ...
Much research has been devoted to B abortus transmission in cattle (Bos taurus)
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From page 17... ...
Examination of mtDNA control-region sequences (691 base pairs) revealed divergence of 0.09 (Bison bison versus Bos taurus)
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From page 18... ...
abortus into their first pregnancy and abort a highly infected placenta. It is the latter group, typically small in a chronically infected herd, that will sustain brucellosis in the herd.
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From page 19... ...
Although more data on bison are neeclecI, it is imprudent to assume a high risk of transmission in bison that are not infected in the reproductive tract or mammary gland. The overriding importance of pregnancy ant!
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From page 20... ...
In sexually mature animals, brucelIae and brucelIainfected cells have a strong tropism for the genital tissues and mammary glands tissues that are needed for efficient replication. It is unlikely that large numbers of bison in a herd would be infected in lymphoid tissues but not in the uterus or mammary glands.
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From page 21... ...
The small numbers of positive bacterial cultures that are obtained from a chronically infected herd do not come from the same individuals; that clearly indicates that the number of infected females is always greater than the number that are shedding or bacteremic at a given time. The assumption is that the reproductive tract is infected, and the rise and fall of genital bacterial numbers are related to unknown stimuli or stress factors.
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From page 22... ...
Transmission, if it occurs, might be insufficient to maintain brucellosis in any animal population. Although fetal membranes and fluids can contain the massive amounts of bacteria that effectively promote transmission, tissues of aborted bison fetuses are also highly infectious for predators.
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From page 23... ...
Shedding in Mammary Glands and Milk An important exception to the low risk of transmission concerns the mamma~y gland, which is not anatomically part of the reproductive tract.
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From page 24... ...
Because copraphagous animals couicl be infected by eating bison feces, fecal excretion that results from infection of intestinal tissue particularly the lymphoic] tissue of the ileum and colon-cannot be ruled out.
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From page 25... ...
Although it can occur, venereal transmission probably floes not play a large role in the maintenance of brucellosis in bison in nature. Nonetheless, potential transmission through copulation floes need to be considered for bison cows and clomestic cows, given that bison bulls will serve domestic cows if confiner]
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From page 26... ...
that venereal transmission by an infected bison bull in service of cows in a captive group failed. Artificial insemination studies have shown titan infected semen placed in the uterus often leads to transmission, whereas semen placed in the vagina or cervix usually floes not (Manthei et al.
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From page 27... ...
bacteriologic studies. The cell in the host's lymphoid tissues that perpetuates bacterial growth in chronically infected males and nonpregnant females is not known but is often referred to as the macrophage.
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From page 28... ...
An infected herd is one in which at least one animal has been shown to be infected; the diagnosis is based on results of several serologic tests, bacterial culture results, and information regarding herd history, clinical signs, and epidemiology. Minimal criteria for a diagnostically positive reaction to various serologic tests in cattle are provided by APHIS.
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From page 29... ...
In chronic infection, false-negative reactions occur when bacteria are sequestered in lymphoid tissues in a state that does not induce antibody formation. One problem of brucellosis serology is that some animals do not clear bacteria but retain them in their lymphoid tissues in very small numbers or in an inactive state that does not stimulate precipitating antibodies sufficient to react in serologic tests.
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From page 30... ...
There is a small peak at sexual maturity as the reproductive system is infected and a large increased in late pregnancy as the placenta, fetus, and mammary gland are infected. the sample.
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From page 31... ...
Detection of one or two B abortus in lymphoid tissues of chronically infected animals remains a problem in treat defects in sampling or culture technique often leac!
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From page 32... ...
Current knowledge of serologic reactions to organisms of the genus BrucelIa suggests that although we know that the presence of antibodies in an animal having had brucellosis lasts beyond the point where bacteria have been cleared from the host, it is more probable that any discrepancy between a clearly positive serologic test and bacterial culture is due to culture techniques. Tests designed for cattle have been used for years to detect seropositivit~r in bison, but diagnostic tests used now for cattle have not been validated in bison.
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From page 33... ...
abortus, are used in Europe to diagnose brucellosis in cattle of seronegative herds. In the course of bovine brucellosis, cutaneous reactivity develops later than do antibody responses but persist long after serologic evidence of infection has clisappearec]
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From page 34... ...
by two importantcharacteristics: the validity of data used to establish it, and lack of full knowledge of the factors that skew the MID one way or the other. For example, animals with intercurrent disease that stimulates marked antibody production or cell-mediated responses shown significantly increased immune response tovirulentBrucel/a spp.: calves with severe cutaneous fungal infections, such as ringworm, develop strikingly greater antibociy responses to virulent B
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From page 35... ...
TRUE PREVALENCE OF B ABORTUS IN GYA BISON AND ELK The true prevalence of brucellosis in GYA bison ant]
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From page 36... ...
in 1917, and 40-54% of YNP bison tested have been reported as seropositive since then (GYIBC 19971. Serologic evidence indicates that as many as 60% of YNP bison (Tunnicliffand Marsh 1935, Pac ant!
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From page 37... ...
(Thorpe and Herriges 19921. Such transmission was believed to be extremely unlikely in normal calving on traditional elk calving ranges 2Elk vaccinated at Jackson Hole with strain 19 vaccine have titers that cannot be differentiated in standard serologic tests from those caused by field strains; elk vaccinated with strain RB 51 do not have the confounding serum antibodies.
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From page 38... ...
Herriges 1992~. Serologic evidence of brucellosis has been found in blood samples from elk corralled in 1 ~ of 23 feeding grounds with seropositive rates averaging 37% in adult females (Herriges et al.1991)
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From page 39... ...
abortus biovar 1. No acute phase of disease developed no clinical signs, no abnormal blood values, no abnormal serum .
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From page 40... ...
A second horse user! to pack out hunted elk also had fistulous withers and positive serologic tests; bacterial cultures did not grow B
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From page 41... ...
Brucellosis recently was detected in black bear and grizzly bear in the greater Yellowstone ecosystem (K.
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