Haemorrhagic septicaemia

S S BASTIANELLO AND M M HENTON

GENERAL INTRODUCTION: FACULTATIVELY ANAEROBIC GRAM-NEGATIVE RODS Pasteurella and Mannheimia spp. infections

Introduction and aetiology

Haemorrhagic septicaemia is a peracute to acute, highly fatal bacterial disease, principally of cattle and water buffalo (Bubalus bubalis), in which Pasteurella multocida serotype B or E is the sole causal organism. It is endemic throughout south-east Asia, India and many regions of Africa.^{12, 16, 28} The Asian form is caused by serotype B and the African form (East African haemorrhagic fever) primarily by serotype E.

By means of an indirect haemagglutination test (Carter procedure) P. multocida strains are characterized according to their capsular antigens into five capsular groups (A, B, D, E and F) and, using a gel diffusion test, into 16 somatic types (1 to 16) (Heddlestone procedure).³⁹ Traditionally haemorrhagic septicaemia has been regarded as being caused only by serotype B:2 or E:2 but other strains are recognized as causing it, in particular types B:1 and B:3,4. Both of the latter types have been linked to outbreaks of haemorrhagic septicaemia in the USA whilst B:3,4 was involved in disease among reindeer (Rangifer tarandus) in Lapland and fallow deer (Dama dama) in Denmark and the UK,1, ³⁸ and serotype B:2 has been implicated in an outbreak in cattle in Zimbabwe.^{28, 33}

For further information on the characteristics of Pasteurella spp., consult the introduction to Pasteurella and Mannheimia spp. infections.

Epidemiology

Haemorrhagic septicaemia occurs commonly in several countries in western and eastern Africa, including Senegal, Mali, Ivory Coast, Nigeria, Cameroon, Egypt, Sudan, Congo, Democratic Republic of the Congo and Zambia, and has occasionally occurred in southern Africa in Namibia and Zimbabwe. ^{4, 6, 7, 20, 22, 28, 33, 34, 35, 36, 46} In Asia the disease is especially prevalent in south-east Asia including Indonesia, Philippines, Malaysia and Thailand as well as in India and Sri Lanka.^{12, 16, 17, 30} It has on rare occasions also been recorded in the USA and Canada where in both countries bison (Bison bison) were principally affected.^{27, 31} The disease has also been reported in cattle in Argentina, southern Europe and Russia^{6, 37} and, recently, in cattle, pronghorn (Antilocapra americana) and elk (Alces alces) in the USA and reindeer in Lapland.³⁸

Until recently type E was believed to have been the cause of haemorrhagic septicaemia in all countries in Africa except Egypt and Sudan where both serotype B and E have been implicated8, ^{22, 25} possibly because of the proximity of these two countries to Asia, where only serotype B is involved. Recent outbreaks of the disease in Namibia and Cameroon, however, have been caused by serotype B:2, whilst an outbreak in Zimbabwe in 1990 was caused by B:2.^{20, 32, 47}

In Africa haemorrhagic septicaemia is endemic in the tropical and subtropical regions of several countries in west Africa and the horn of Africa. Outbreaks in these parts tend to be sporadic and may spread to the drier and semi-arid regions of the Sahel when cattle are subjected to stress such as that induced by abnormally wet weather patterns or their migration to other parts.^{22, 36} In southern Africa the disease is very sporadic and mainly restricted to the wetter subtropical regions of Zambia, Zimbabwe and the northern parts of Namibia. In the latter country it occurs particularly in the Caprivi, Ovamboland and, to a lesser extent, Otjiwarongo, Okahandja, Gobabis and Grootfontein districts, although it has also been reported from drier areas such as the Keetmanshoop and Windhoek districts.^{7, 9, 20, 28, 47} The Zimbabwe outbreak, which was severe, occurred in the unusually wet and cold summer of 1990 on a farm irrigated with sewage effluent.²⁸ There is only one record of the disease occurring in South Africa where it involved calves in the relatively dry but hot North West Province.⁸

The Asian form of haemorrhagic septicaemia occurs in countries with a high seasonal rainfall where it is frequently endemic in marshy zones or along river deltas.³⁶

In the endemic regions of both Asia and Africa, haemorrhagic septicaemia occurs throughout the year but its prevalence increases at the onset of, or during, the rainy season when it tends to spread, presumably due to a longer survival time of the organism in damp conditions.^{4, 5, 17, 19, 22} It has been reported to occur following a sudden increase in rainfall and humidity with a concomitant severe drop in temperature. ⁴ The outbreaks which occurred in Namibia in 1994 and 1995 were not associated with increased environmental moisture but took place in winter when the affected cattle were subjected to severe cold and stress associated with confinement.⁴⁷

Under natural conditions, haemorrhagic septicaemia occurs mainly in cattle and water buffalo but it has also been reported in pigs, sheep, horses, donkeys, camels, fallow deer, bison and Indian elephant (Elephas sengalensis).^{3, 7, 12} Water buffalo are more susceptible than cattle,^{12, 24} the mortality rate in Sri Lanka being three times greater in water buffalo than in cattle.¹⁶ The disease has been reported in goats in India and Malaysia,16 but in Sri Lanka they were found to be highly resistant to experimental infection; after being inoculated with large numbers of the causative organism they developed neither the disease nor any detectable immunity. ^{16, 17}