This study evaluated the presence of selected heavy metals in farmed tilapia and catfish) in Nyeri County, Kenya. Live fish comprising of 17 catfish and 33 tilapias were purchased from 15 fish farmers with 31(62%) caught from earthen ponds while 19 (38%) were from liner ponds. The fish were dissected to obtain muscle tissue samples for analysis for levels of lead, mercury and cadmium residues using the Flame Atomic Absorption Spectrometry. Tilapia fish accumulated higher concentrations of lead, mercury and cadmium in the muscles compared to catfish. The difference of lead and mercury ion concentration between fish species was not significant (p>0.05). Fish obtained from earthen ponds recorded a higher mean concentration of the three heavy metals compared to those from liner ponds. Mercury concentration in fish muscles was slightly higher than European Union limits (0.1 Mg/Kg) but lower than codex alimentarius (0.5 Mg/Kg) limits. There is need to continuously monitor levels of heavy metals especially mercury in farmed fish tissues in Nyeri County and other peri-urban areas in Kenya.
An investigation on vegetation was carried out in one grazing paddock of the University of Nairobi, Veterinary Farm to establish the species of plants present and whether some were known to be poisonous. This investigation was carried out after reported cases of young dairy cattle manifesting signs of acute toxicity shortly after being grazed in this paddock. A checklist of the floristic composition of the site was exhaustively recorded and thirty two plant species were collected from the site. Five out of thirty two plants were suspected to be the possible cause of this poisoning as they have been reported before to have toxic effects. These were botanically identified as Ranunculus multifidus Forsk, Cassia didymobotrya Fres, Ricinus communis L., Datura stramonium L. and Momordica foetida Schum. It is concluded that some of these plants may be responsible for the poisoning and further studies on their level of toxicity and distribution in the farm needs to be determined.
Nicandra physaloides (L) Gaertn (Solanaceae), commonly known as the 'apple of Peru' is widely associated with livestock poisoning. The clinical signs associated with its poisoning in ruminants appear within 6 hours of ingestion and are circling, tremors of the hind limbs, tachycardia, bloat, convulsions, coma and death. However, there is no published information on the toxicology of this plant in Kenya. This study documents Nicandra physaloides toxicity in two different zerograzed dairy cattle herds that were inadvertently fed on Napier grass contaminated with Nicandra physaloides. In addition to the case studies, the toxicity of the aqueous extracts from the different parts of Nicandra physaloides was studied under experimental conditions in mice. The 24 hour median lethal dose (LD50) was determined after intra-peritoneal injection (i.p.) of the aqueous extracts of the plant into white Swiss mice and found to be 1820, 2580 and 3620 mg/kg body weight for the leaves, fruits and whole plant respectively. The clinical signs in mice appeared within 30 minutes of inoculation and included coat, decreased locomotor activity, increased respiratory rate, gasping for air and leaping into the air before collapsing into coma and death. There were similarities in the symptoms of the spontaneous poisoning in cattle and in the experimentally induced poisoning in mice.
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