ETIOLOGY

Classification of the causative agent

Virus family Paramyxoviridae, genus Morbillivirus

Resistance to physical and chemical action

Temperature: Small amounts of virus resist 56°C/60 min or 60°C/30 min

pH: Stable between pH 4.0 and 10.0

Chemicals: Susceptible to lipid solvents

Disinfectants:      Susceptible to most common disinfectants (phenol, cresol, sodium hydroxide 2%/24 hours used at a rate of 1 litre/m2)

Survival:      Remains viable for long periods in chilled or frozen tissues

EPIDEMIOLOGY

  1. High morbidity rate, mortality rate is high with virulent strains but variable with mild strains

Hosts

  1. Cattle, zebus, water buffaloes and many species of wild animals: African buffaloes, eland, kudu, wilde-beest, various antelopes, bushpigs, warthog, giraffes, etc.
  2. Sheep, goats are susceptible
  3. Asian pigs seem more susceptible than African and European pigs
  4. Rinderpest is rare among camelidae
No age- or sex-linked predisposition

Transmission

   1. By direct or close indirect contacts

Sources of virus

   1. Shedding of virus begins 1-2 days before pyrexia in tears, nasal secretions, saliva, urine and faeces
   2. Blood and all tissues are infectious before the appearance of clinical signs
   3. Infection is via the epithelium of the upper or lower respiratory tract
   4. No carrier state

Occurrence

The virus has never established itself in the Americas or Australia/New Zealand. Its distribution in other parts of the world is restricted. In Africa it has been eradicated from several countries and sub-regions, and is normally absent from the northern and southern parts of the continent. Rinderpest occurs in the Middle East and in southwestern and central Asia For detailed information on occurrence, see recent issues of World Animal Health and the OIE Bulletin

DIAGNOSIS

Incubation period is 3-15 days

Clinical diagnosis

Classic form: four stages

  • Incubation period
  • Febrile period (40-42°C) with depression, anorexia, reduction of rumination, increase of respiratory and cardiac rate
  • Mucous membrane congestion (oral, nasal, ocular and genital tract mucosae)
  • intense mucopurulent lachrymation and abundant salivation
  • anorexia – necrosis and erosion of the oral mucosae
  • this phase lasts 2-3 days
  • Gastrointestinal signs appear when the fever drops: profuse haemorrhagic culars containing mucus and necrotic debris. Severe tenesmus. Dehydration, abdominal pain, abdominal respiration, weakness, recumbency and death within 8-12 days. In rare cases, clinical signs regress by day 10 and recovery occurs by day 20-25

Peracute form

No prodromal signs, high fever (>40-42°C), sometimes congested mucous membranes, and death. This form occurs in highly susceptible young and newborn animals

Subacute form

Clinical signs limited to one or more of the classic signs. Low mortality rate

Atypical form

Irregular pyrexia and mild or no diarrheoa. The lymphotropic nature of rinderpest virus favours recrudescence of latent infections and/or increased susceptibility to other infectious agents

Sheep, goats and pigs

  • Variable pyrexia and anorexia
  • Inconsistent culars

Pigs

Pyrexia, prostration, conjunctivitis, erosions of buccal mucosa, death

Lesions

  • Either areas of necrosis and erosions, or congestion and haemorrhage in the mouth, intestines and upper respiratory tracts
  • Enlarged and oedematous lymph nodes
  • White necrotic foci in Pepyer’s patches
  • Zebra striping’ in the large intestine
  • Carcass emaciation and dehydration

Differential diagnosis

Cattle

  •  Foot and mouth disease
  •  Bovine viral culars/mucosal disease
  • Infectious bovine rhinotracheitis
  • Malignant catarrhal fever
  • Vesicular stomatitis
  • Salmonellosis
  • Necrobacillosis
  • Paratuberculosis
  • Arsenic poisoning

Small ruminants

Peste des petits ruminants

Laboratory diagnosis

Procedures

Identification of the agent

Antigen detection

  • Agar gel immunodiffusion test
  • Direct and indirect immunoperoxidase tests
  • Counter immunoelectrophoresis
  •  Immunohistopathology

Virus isolation and identification

  • Virus isolation
  • Virus cularsisd  in VERO or bovine kidney cell cultures
  • Immunoperoxidase staining

Virus RNA detection

  • Rinderpest-specific cDNA probes
  • Amplification by polymerase chain reaction (PCR

Serological tests

  •  ELISA
  • Virus cularsisd

Samples

  • Sterile whole blood preserved in heparin (10 IU/ml) or EDTA (0.5 mg/ml) and transferred to laboratory on ice (but not frozen)
  • Spleen, prescapular or mesenteric lymph nodes of dead animals chilled to sub-zero temperatures
  • Ocular and nasal secretions of infected animals during either the prodromal or the erosive phase

PREVENTION AND CONTROL

No treatment

Sanitary prophylaxis

  • Isolation or slaughtering of sick and in-contact animals
  • Destruction of cadavers
  • Disinfection
  • Protection of free zones

Medical prophylaxis

  • Cell-culture attenuated virus vaccines are highly effective
  • The commonly used vaccine is an attenuated strain of rinderpest virus. In some countries a mixed rinderpest/contagious bovine pleuropneumonia vaccine is used
  • Immunity lasts at least 5 years and is probably life-long. Annual revaccination is recommended in order to obtain a high percentage of culars animals in an area
  • Genetically engineered thermostable recombinant vaccines are currently undergoing limited field trials