Sheep and goats in southwest Nigeria are carrying bacteria that are resistant to a range of drugs, such as antibiotics. This is a problem because the bacterium, methicillin-resistant Staphylococcus aureus, poses a potential health risk to the owners as well as to the general population.
People can be infected with the bacterium if they come into direct contact with animals carrying it, or materials contaminated with it. This can lead to severe infections like food poisoning.
In addition, managing methicillin-resistant Staphylococcus aureus has been compromised by the fact that farmers are using antibiotics indiscriminately. This has, in turn, led to a rise in drug resistance.
Sheep and goats are important in Nigeria as sources of meat and milk. They are also household assets. They contribute about 35% of the total meat consumed in Nigeria. Goat milk is also consumed in some parts of Nigeria, especially Borno State in the northeast.
One of the main diseases in sheep and goats caused by the bacterium is mastitis, which affects milk production and weight gain. It can also contaminate milk and be harmful to humans.
Mastitis is the inflammation of the udders – mammary glands of cows, sheep and goats. It may be clinical and subclinical. Subclinical means it is not severe enough to present definite or readily observable symptoms. The presence of pathogenic organisms in the milk is only detectable using very specific tests.
In our study, we investigated the prevalence of methicillin resistant Staphylococcus aureus in goat and sheep milk and nasal samples in Abeokuta, southwest Nigeria.
Previous studies conducted in the northern part of Nigeria showed that it was prevalent in goat and sheep milk. But no similar work had been conducted in the southern region.
What we found
In total, 400 samples made up of 200 raw milk samples and 200 nasal swabs were collected from small ruminants (females only) from 10 locations in Abeokuta. Three stages were involved in the analysis of the samples. The first was the isolation and cultivation of the bacterium from the samples (nasal and milk). This was done by dispensing small volumes of the milk samples and nasal swabs in enrichment broth and then on solid media to recover the bacterium.
The second stage involved identifying the isolated bacterium using biochemical tests that can differentiate the organism of interest from other bacteria. After the organisms had been identified as Staphylococcus aureus, they were tested against two antibiotics. These were cefoxitin and oxacillin. The aim was to confirm if they were methicillin resistant or not.
In the third stage, the methicillin-resistant Staphylococcus aureus isolates were tested against 10 commonly used antibiotics in the study area.
From our result, the prevalence rates detected in raw milk and nasal swab were higher than previous studies in the northern part of Nigeria. This finding corroborates the fact that the methicillin-resistant Staphylococcus aureus population is rising and spreading among small ruminants in Nigeria.
Why this matters
This poses a serious threat to the general wellbeing of humans. Those particularly at risk are animal professionals, butchers, veterinarians, animal handlers and slaughterhouse workers having direct contact with the animals or their products.
The bacteria were also resistant to the antibiotics commonly used in the study area. The isolates showed resistance to ampicillin, cloxacillin, sulphamethoxazole-trimethoprim, amoxicillin-clavulanate, ceftriaxone, cefuroxime and erythromycin but were sensitive to streptomycin, ciprofloxacin, pefloxacin and gentamicin.
The presence of multidrug-resistant bacteria in small ruminants reared in Abeokuta metropolis may be due to indiscriminate use of antibiotics and unhygienic practices by farmers. Antibiotics are readily available, cheap and accessible at any animal store.
Next steps
Mastitis caused by methicillin-resistant Staphylococcus aureus should be eliminated because of the severity of clinical symptoms, antibiotic resistance and the risk of contamination of milk products by toxins. The toxins can cause food poisoning in humans, if contaminated and unpasteurised milk is consumed. The usual symptoms are nausea, vomiting, diarrhoea and stomach cramps.
We recommend that farmers who rear small ruminants should ensure strict hygiene. Proper housing for the animals should be in place. Also, thorough washing of hands before and after milking or feeding is advised.
Only pasteurised milk and milk products should be consumed. Government should enforce laws prohibiting the indiscriminate use of antibiotics in small ruminants by farmers without veterinarian prescriptions.
