History
Investigation
Treatment
Results
Discussion
Bibliography
SHORT COMMUNICATIONS
P.A Onyeyili, G.A. Chibuzo, F. Brisibe and G.O. Egwu
The authors can be contacted at the Faculty of Veterinary Medicine, University of Maiduguri, PMB 1069, Maiduguri, Nigeria.
Nigeria is a vast country extending from the Atlantic Ocean in the south, with thick mangrove and tropical rain forests, to the dry savannah grassland and more arid Sahelian region in the north. The arid zone of Borno State is a main centre of the livestock industry in Nigeria usually during the long annual dry season (from November to June) and particularly during the periodic droughts. Much of the land is overgrazed (Figure 1), with the livestock having insufficient palatable forage even during the early rainy season. Only trees with extensive root systems capable of reaching deep down to obtain water and with little water requirement, such as baobab, acacia and Balanites aegyptiaca, survive in this region.
Nomadism is a prominent factor in animal husbandry in Nigeria, where the search for grazing results in the animals changing environments and vegetation. Animals that are unfamiliar with the plants in the new environment are likely to be poisoned (Adaudi, 1975; Nwude and Parsons, 1977). Although there are potentially many poisonous plants in Nigeria, only a few known to-cause poisoning in animals have been reported (Anon., 1937; Mettam, 1941; Anon., 1956; Na'Isa, 1969; Nwude and Parsons, 1977; Adaudi, 1975). There have been no reported cases of toxicity from death-camus (Zypadenus spp.) (Figure 2) in the environment, although an outbreak of poisoning did occur in July 1984 in the village of Kayi-Yari, about 15 km north of Tere, Maiduguri metropolis. Death-camus of the lily family is stunted during the dry season but bursts into full bloom after the first rains and is toxic if consumed.
The mass deaths in July 1984 of 2 490 sheep from nine flocks (mainly of the Uda breed) in Kayi-Yari village attracted the attention of a staff member of the Ministry of Agriculture who reported the incident to the Public Health Office of the Federal Livestock Department unit in Maiduguri. The Borno State Ministry of Animal and Forestry Resources and the Faculty of Veterinary Medicine, University of Maiduguri, were informed immediately. The affected flocks belonged to herders travelling from Legone in Cameroon through the border town of Banki to the villages of Bama, Konduga, Kayi-Yari, Gaji-Gana and Gubio in Nigeria, where they were expected to graze for the rest of the rainy season. This first outbreak was followed by a second one a week later, which caused the deaths of a further 620 sheep from four flocks.
All animals showed the following clinical signs: salivation, weakness, ataxy and discharges from oral and nasal cavities. They were later slaughtered for consumption to curtail further losses and all the gastrointestinal tracts, livers, kidneys and lungs were condemned.
Upon interrogation of the Fulani herders it appeared that they were unfamiliar with the area containing death-camus. There was also evidence of starvation in the flocks because of insufficient availability of grass. Further questioning revealed that large numbers of sheep had already grazed on the lush outgrowth that was relatively abundant before the high mortality in the flocks was noticed.
Some of the affected sheep were physically examined and postmortems were performed on some of the dead animals. Specimens of the plant were also collected for identification. Since the outbreaks nine years ago, the area with the toxic plants has been under observation to determine the toxicity of the plant to indigenous sheep. The restricted movement of herders and their animals across the Nigerian border to prevent outbreaks of transmissible diseases such as rinderpest has also limited the presence of exotic sheep in the area.
A broad-spectrum antibiotic (Terramycin Long Acting) was administered to combat secondary bacterial infection, and a steroid was also given in some cases to reduce systemic toxicity. The surviving animals were moved to another location and given adequate supplementary feed.
The toxic plant was identified as Zygadenus chlorantus. Most of the poisoned animals were severely emaciated. Post-mortem examinations revealed widespread petechial and ecchymotic haemorrhages on the bronchial mucous membrane, pleura, pericardium and endocardium. The intestines showed diffused areas of haemorrhages, while subcapsular haemorrhages were observed in the kidneys. The liver was observed to be friable and congested. The lungs were also congested and excess fluid was observed within the gastrointestinal tract.
The Table shows the percentage mortality rate observed from the two outbreaks. The first outbreak involved a total population of 2 490 sheep and produced 2 000 deaths, while in the second outbreak 256 animals died out of a total population of 620.
There was marked improvement in the general condition of the sheep, with mortality reduced to a minimum, when the herders moved to safer areas.
Mortality in sheep during the first and second outbreaks following ingestion of death-camus - Taux de mortalité des moutons durant la première et la seconde épidémie après ingestion de zygadène - Mortalidad de los ovinos durante el primero y segundo brotes, tras la ingestión de camus de la muerte
|
Flock number of sheep |
Number of dead |
Number of mortality |
Percentage |
|
First outbreak |
|
|
|
|
1 |
400 |
320 |
80 |
|
2 |
300 |
230 |
77 |
|
3 |
100 |
60 |
60 |
|
4 |
100 |
50 |
50 |
|
5 |
110 |
50 |
45 |
|
6 |
200 |
130 |
65 |
|
7 |
180 |
120 |
67 |
|
8 |
100 |
40 |
40 |
|
9 |
1 000 |
1 000 |
100 |
|
Total |
2 490 |
2 000 |
80 |
|
Second outbreak |
|
|
|
|
1 |
255 |
135 |
53 |
|
2 |
138 |
38 |
28 |
|
3 |
85 |
35 |
41 |
|
4 |
142 |
48 |
34 |
|
Total |
620 |
256 |
39 |
It was observed that sheep of sedentary flocks in and around the village of Kayi-Yari were not lost from the specific poisoning and that resident sheep were not observed to have consumed the toxigenic plant. A determining factor in cases of animal poisoning resulting from toxigenic plants is hunger. The familiarity of the herders and their animals with the poisonous plants through prior association (Nwude and Parsons, 1977) seems to be the plausible explanation for the indigenous sheep not having been affected in this case of poisoning, while the "exotic" sheep unfamiliar with the environment were poisoned. The closing of the country's international borders with the sole aim of curtailing the migration of herders and their livestock into the country has greatly limited the exposure of exotic animals to this unfamiliar terrain where the poisonous plants abound. As a result, no poisoning of exotic animals has been reported since the outbreaks under discussion. Furthermore, no indigenous sheep in the area have been reported to have been poisoned by the plant despite the fact that these plants still flourish in the location.
The nomadic system of animal husbandry, which is closely linked to the search for lush pastures in order to satisfy demands for forage in areas where climatic conditions and pasture management practices do not guarantee its availability, is an important condition favouring poisoning by toxic plants.
The herders' compliance to the advice that they vacate the area with the toxic plant was most likely responsible for the lower mean mortality rate of 41 percent (from 33.80 to 52.94 percent) in the second outbreak, compared with the overall mortality rate of 80 percent (from 40 to 100 percent) recorded for the first outbreak (see Table). This advice agrees with the view of Nwude (1990), that animals should be prevented from grazing in areas where the eradication of toxic plants is not feasible.
Zygadenus spp. (death-camus) had never been identified scientifically in Nigeria until this case of poisoning occurred. The plant, which belongs to the Liliaceae family, contains complex alkaloids, including zygacine, zygadine and zygadenine (Kingsbury, 1964; Radeleff, 1970). Well known by the natives as Jedel (Kanuri name), this plant produces gastrointestinal and neurological symptoms similar to those recorded by Clarke and Clarke (1975). It is one of the few plants that sprout immediately after the first rains, and animals are therefore tempted to graze it during this time when other green vegetation is scarce.
The possibility of toxic residues remaining in the edible tissue of affected animals exists and human poisoning may occur through the consumption of their products (Kingsbury, 1964; Schoental, 1965). This study did not investigate whether actual poisoning did occur in humans as a result of concentrations in animal tissue, however, it does stress the importance of poisonous plants for the livestock industry in Nigeria. The public health and economic implications of this type of outbreak are immense. Massive losses of this nature affect the animal-protein supply of the nation, which is of great significance in a developing country such as Nigeria, where animal protein is very much needed to improve the health of the population.
Adaudi, A.O. 1975. Dichapetalurm barteri poisoning in goats. Trop. Anim. Health Prod., 7: 56-57.
Anon. 1937. Annual report of Veterinary Department of Nigeria, 1936. p. 22.
Anon. 1956. Annual report. Zaria Province. District Veterinary Service. Northern Region. p. 10.
Clarke, E.G.C. & Clarke, M.L. 1975. Veterinary toxicology, p. 340-341. New York, NY, USA, MacMillan Publishing Company, Inc.
Kingsbury, L.M. 1964. Poisonous plants of the United States and Canada, p. 9. Englewood, NJ, USA, Prentice Hall, Inc.
Mettam, R.W.M. 1941. Plant poisoning in domestic animals. Farm Forest., 1: 58-62.
Na'Isa, B.K. 1969. The protection of 60 Nigerian trade cattle from trypanosomiasis using samorin. Bull. Epizoot. Dis. Afr., 17: 45-54.
Nwude, N. 1990. Toxicological problems on range and sown pastures. Paper presented at Workshop on Range and Pasture Management, Shika-Zaria, Nigeria, 24-29 September 1990.
Nwude, N. & Parsons, L.E. 1977. Nigerian plants that may cause poisoning in livestock. Vet. Bull., 47: 811-817.
Radeleff, R.D. 1970. Veterinary toxicology, 2nd ed. Philadelphia, PA, USA, Lea and Febiger.
Schoental, F. 1965. Toxicology of natural products. Far East Med. J., 1: 291-296.
