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Bacterial Disease - Listeriosis

Synonyms: Silage disease, Circling diseases and Listerellosis

Introduction:

Listeriosis is a sporadic bacterial infection that affects a wide range of animals, including man and birds. It is seen worldwide, more frequently in temperate and colder climates. There is a high incidence of intestinal carriers. Encephalitis or meningoencephalitis in adult ruminants is the most frequently recognized form.

Etiology and Epidemiology

Listeria monocytogenes is a small, motile, gram-positive, non-spore-forming, extremely resistant, diphtheriod cocco-bacillus that grows under a wide temperature range, 39-111 F (4-44°C). Its ability to grow at 4°C is an important diagnostic aid (in the "cold enrichment" method) for isolation of the organism from brain tissue (but not from placental or fetal tissue).

The natural reservoirs of L.monocytogenes appear to be soil an mammalian GI tracts, both of which contaminate Vegetation. Grazing animals ingest the organism and further contaminate vegetation and soil. Animal-to-animal transmission occurs via the fecal-oral route. Listeriosis is primarily a winter-spring disease of feedlot or housed ruminants.

Host

Listeriosis is primarily a disease of ruminants' particularly sheep, and the major diseases associated with L. monocytogencs are encephalitis and abortion. In ruminants it also produces syndromes of septicemia, spinal myelitis, uveitis, gastroenteritis, and mastitis. Occasional septicemic disease occurs in horses and pigs.

Pathogenesis

Listerias that are ingested or inhaled tend to cause septicemia, abortion, and latent infection. Those that gain entry to tissues have a predilection to localize in the intestinal wall, medulla oblongata, and placenta or to cause encephalitis via minute wounds in buccal mucosa or via inhalation or the conjunctiva.

Clinical signs

Sheep and goats

In early infection, affected sheep separate from flocks, show high temperature 40ºC, cranial nerve dysfunction, run and fall in a flaccid motion .

More acute death in 2-4 days of infection.

Affected animals develops in-coordination, head deviation, head tilting, wallowing in circles, unilateral facial hypalgisia, paralysis of lips and face.

Keratitis, corneal ulceration, strabismus, nystagmus, panopthalmitis with pus evident in anterior chamber of one or both eyes.

Paresis of muscles of the jaw, dropped jaw which ensues difficulty in prehension and mastication.

Poll-nose relationship, recumbent, death due to respiratory failure.

In young ones onset is sudden and the course of the disease is short. Death occurs in 2-3 days.

Abortion occurs in 3 months of pregnancy. Abortion is as high as 15% with annual recurrence.

Retained placental membrane, mortality in ewes in case of foetus retention.

Abortion due to L. ivanovii is sporadic in cattle. In sheep and goats causes outbreak, still birth and birth of live infected lambs.

Cattle

Course of the disease in adult cattle is 1-2 weeks and in calves disease is more acute and death follows in 2-4 days.

Fever 40.5ºC, abortion, still birth (sporadic) usually occurs in last trimester of pregnancy, retained placental membrane,

Abortion seen after silage feeding.

Encephalitis signs include circling, ptosis, half chewed food in the mouth and unilateral facial paralysis.

Septicemic listeriosis

Acute septicaemia - L. monocytogenes is not common in adult ruminants. No nervous signs but depression, weakness, emaciation, pyrexia, diarrhoea, hepatic necrosis and gastroenteritis.

Corneal opacity, dyspnoea, nystagamus and mild opisthotonus is noticed.

Death occurs in 12 hours following infection.

At necropsy, opthalmitis, serofibrinous meningitis observed.

Septicaemia is also recorded in foals.

Inflammation of single quarter or both quarter.

Chronic mastitis show poor response to treatment, high somatic cell count in milk but milk appears normal.

Septic myelitis

Fever, ataxia, initial knuckling of hind limbs, weakness, and paralysis.

No cranial nerve involved.

Animals affected appear to be alert, bright and eat well.

Opthalmitis

Iritis: Swelling of iris, constriction of pupil. Advanced cases, pannus and corneal opacity may be uni/bilateral.

Enteritis

Weaner sheep : Initially found dead. Lethargy, anorexia, pass loose green coloured faeces. Pregnant ewes may abort.

Clinical pathology

Culture. Pleocytosis and elevated protein in cerebrospinal fluid with encephalitis

Lesions

Micro abscesses in brainstem in listerial encephalitis, spinal cord in spinal myelitis, intestine in enteritis. Visceral lesions in septicemia

Diagnostic confirmation

Culture and histopathology

Differential diagnosis

Pregnancy toxaemia. in sheep.

Nervous ketosis, rabies, kid, polioencephalomalacia, middle ear disease and scrapie in cattle.

Trichomoniasis.

Brucellosis.

Toxoplasmosis.

IBRT.

Salmonellosis.

Contagious opthalmia.

Vaginal secretions, abortion, milk, faeces, tonsils, cerebrospinal fluid, mid sagittary section of brain, brain stem (chilled or frozen), formalin fixed spinal cord segment.

Treatment

Chlortetracycline -10mg/kg BW/day for 5 days for meningo-encephalitis for Cattle

Inj. Penicillin-44000 IU/kg BW, I/M daily for 7 days or 10-14 days.

Supportive therapy

Control

Control of listerial growth in feeds. Vaccination

Live attenuated vaccine shown to induce protection.

Commercial killed vaccine available.


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