Better Pork - June 2016

Better Pork

June 2016

HERD

HEALTH

Brucellosis (Brucella suis)

Brucellosis is a bacterial disease caused

by species of the bacterium

Brucella spp.

It was first isolated by Sir David Bruce

who found it in British soldiers who had

died with undulant fever (also called

Malta fever, Mediterranean fever and

Bang’s disease) in Malta in 1885. The or-

ganism that was isolated,

Brucella meli-

tensis

, was endemic in sheep and goats

in Malta and the source of zoonotic

transmission of the disease to humans.

Although Sir David Bruce isolated B.

melitensis, the cause of Malta fever,

there are several other species of

Bru-

cella

that cause disease in humans and

animals, including

B. abortus

(cattle),

suis

(pigs),

B. ovis

(sheep) and

B. canis

(dogs). In cattle, pigs and other animals,

the bacterium causes abortion and

serves as a source for zoonotic transmis-

sion of these bacteria to humans.

Clinical signs.

Clinical signs are not

seen with

Brucella suis

infection in pigs,

but infection results in stillbirths and

abortions in sows and infertility in both

sexes. In boars, infection in the testicles

and accessory sex glands is common.

Infection is introduced into a herd by

live infected pigs, by contaminated meat

products or by semen or ova during

artificial insemination (AI). Infected

boars are the usual source of infection

within a herd and transmit the disease

by natural service or via AI.

Early abortion (returns to estrus

five-to-eight weeks after service) results

from infection at service, but infection

later in pregnancy produces litters with

mummified, stillborn or weak piglets.

Copious bloody vulval discharges occur.

Testicular swelling—inflammation of

the testicles (orchitis)—may occur in

boars within seven weeks of infection.

Bones and joints may be involved in

both sexes.

Pathogenesis. Brucella

spp. invade

through mucosal surfaces. Successful

invasion usually occurs through the

digestive (intestinal) or respiratory tract.

After successful invasion,

Brucella

spp.

becomes an intracellular organism,

surviving within host cells and evad-

ing protective mechanisms designed to

destroy the bacterium.

Brucella

spp. in-

vade silently and do not elicit a marked

host inflammatory response, but cause

placentitis, fetal death and abortion.

Diagnosis

. Isolation of the organism

and serological (blood) tests are used

for the diagnosis of brucellosis. Vac-

cination and treatment are not 100 per

cent effective, so slaughter followed by

restocking with uninfected stock is the

most successful method of control.

The Canadian swine herd was

declared brucellosis-free more than 30

years ago and has remained so since

1985. Brucellosis, however, is common

in black bears in Canada and remains a

source of infection of hunters and others

who come into contact with the bears.

Erysipelas (Erysipelothrix rhusiopathiae)

Erysipelas occurs worldwide wherever

pigs are reared. Incidence of the disease

has diminished significantly in Canada

since we moved to indoor, confinement-

rearing systems.

The organism

E. rhusiopathiae

present in soil contaminated with feces

and urine from infected or carrier

animals and is present on the tonsils of

clinically normal pigs. The organism

invades a susceptible pig via the tonsils,

gastrointestinal tract or minute skin

cuts. Once inside, it multiplies, creating

a septicemia within one-to-seven days.

Septicemia usually results in fever

and subsequent localization of the

bacterium in the skin, joints, muscle

or valves of the heart. Localization in

joints and heart valves leads to arthritis

and valvular endocarditis, respectively.

Abortion in sows is believed to be a

result of fever.

Erysipelas occurs worldwide wherever pigs are reared. Incidence of the disease has diminished

significantly in Canada since we moved to indoor, confinement-rearing systems.