Antimicrobials if not used judiciously, may have impact on human, animal and environmental health in a One Health context, as up to 90% of the antibiotic parent compounds can be directly excreted in milk and meat leading to antibiotic resistance development in the environment
(Daniel et al., 2014; Boeckel et al., 2017).
Besides, a 2015 study revealed that global agricultural antibiotic usage will increase by 67% from 2010 to 2030, mainly from increase in use in developing BRIC countries. This is a matter of concern as antibiotic resistance is considered to be a serious threat to human and animals and growing levels of antibiotics or antibiotic-resistant bacteria in the environment could increase the numbers of drug-resistant infections. However, legislation and other restrictions on antibiotic usage in farm animals are now being introduced across the globe (
OECD, Paris, 2019). In 2017, the World Health Organization strongly suggested reducing antibiotic use in animals used for food purposes. The occurrence of antimicrobial residues in foods of animal origin, together with failure to observe the instructions and precautions in their usage (dosage and waiting period) or poor livestock production practices, can have deleterious consequences for consumer health
(Hsieh et al., 2011). The regulations for veterinary drugs define a risk assessment protocol to assess their active ingredients and set maximum residue limits (MRLs). Indeed, sustainable livestock systems in developing countries must agree the demand for animal products without compromising people’s future nutritional needs or harming the environment.
The origin of residues in meat and milk
As intramammary infusions deliver high concentrations of antibiotics directly into the mammary gland, the majority of intramammary infusions contain penicillin or other beta-lactam antibiotics and many testing methods are particularly sensitive for this class of antibiotics, it is not astonishing that beta-lactam antibiotics are the most routinely detected residues in milk in most countries. Sulfa drugs are less commonly detected while tetracyclines, aminoglycosides, macrolides and other classes of antibiotics are hardly detected in milk (
Heeschen and Suhren, 1996). While several factors have lead to the residue problem such as poor treatment records or inability to identify treated animals, most violations occur from the usage of a drug in some manner that does not comply with the labeling (
Sundlof, 1989;
Paige, 1994). This occurs basically through not observing withdrawal times as well as “extra-label” use of the drug. Treatments involving any other method than what is written on the product label (
e.
g., different species, increased dosage, different route of administration, different frequency of treatment) are recognized as extra-label usage and withdrawal times are difficult or impossible to determine in these circumastances
(McEwen et al., 1991). Excessive usage of antibiotics has caused xenobiotic residue occurrence in milk and milk products including meat and due to this milk and other food products like meat adulterated with antibiotics beyond a safe level are deemed to be unfit for human use
(Hillerton et al., 1999).
Detection of antibiotic and anthelmintic drug residues in milk samples from market
The above validated methods (Fig 1 and Fig 2) proved successful to detect and quantify the given veterinary drug residues thus indicating that the applied method was appropriate for the detection of antibiotic and anthelmintic residues in milk therefore the standardized and validated method was used for the analysis of total of 60 milk samples randomly collected from the market. Some of the representative chromatograms of anthelmintic residues in milk have been depicted in Fig 3, 4 and 5. The results are summarized in Table 3.
Comparison of levels of antibiotic and anthelmintic residues in milk samples with MRLs
The concentration of antibiotic and anthelmintic residues determined in each of milk and meat samples was compared with the tolerance limit (MRL) set forth by the International Regulatory Authorities MRLs given by European Union Commission (
EU, 2010) and Codex Alementarius Commission of WHO (
Codex, 2015). The results are shown below in Table 4.
Drugs are used frequently in animal husbandry and the presence of drugs in foods like milk and meat is a health risk according to international food and drug regulation rules. Worldwide consumption of antimicrobials in food animal production was estimated at 63151 (±1560) tons in 2010 out of which India shared 3 % and was ranked at 4
th position
(Boeckel et al., 2015). This is an indicator that how higher chances of drug accumulation within animal tissues (meat and milk) were becoming inevitable particularly in a rural Country like India where Food and Drug Regulatory rules regarding veterinary area are very poor. Antibiotic residues in food have a deleterious effect on health and lead to the emergence of antibiotic resistant genes (
Hassan, 2014). The occurrence of antibiotic residues in milk causes hindrance in the preparation of fermented dairy products (
Mayra-Makinen, 1995;
Hays, 2003;
Jones, 2009). The detection and analysis of drug residues in foods like milk, meat, chicken is a topic of urgent nature due to its impact on one health.
Boultif et al., (2024) studied ELISA based monitoring and quantification of tetracycline residues in fresh and powdered cow milk from Algeria.
Al-Kindi et al., (2023) and
Debbarma et al., (2025) have studied the antibiotic residues in Oman and Guwahati, India. It is extremely difficult under rural conditions in India to observe withdrawl periods in terms of veterinary drugs administered for disease treatment.
Detection and analysis of antibiotics and anthelmintics in market milk
In the present study none of the milk sample was detected positive for tetracycline, Oxytetracycline, enrofloxacin and ceftriaxone residues.
Anthelmintics (Ivermectin and Fenbendazole)
Ivermectin is a potent antiparasitic agent derived from naturally occurring fermentation products
(Miwa et al., 1983). Ivermectin is a member of a class of naturally occurring macrocyclic lactones called avermectins. Tissue distribution of ivermectin residues in cattle and sheep have been investigated
(Tway et al., 1981). Although ivermectin has a wide safety range in anthelmintic treatment (
Ayres and Almeida, 2002) some of its excretion occurs through the mammary gland
(Flajs et al., 2005). The presence of ivermectin residues in foods may cause mutagenic effects in some mammalian species (
Ema, 2004). The Codex alimentarius/European Union has set the residue limit of ivermectin in milk at 10 µg/L (
FAO/WHO, 1993). Fenbendazole belonging to benzimidazole class of anthelmintics are mostly used in veterinary sector. In the present study 4 samples of milk amounting to 6.67% and 6 samples amounting to 10% of milk samples were found positive with Ivermectin and Fenbendazole residues respectively (Table 3).
Alvinerie et al., (1987) in France subcutaneously gave ivermectin in a cow and studied the presence of ivermectin in milk for about three weeks through high performance liquid chromatography. This confirmed that avermectins which are very highly used in veterinary medical sector as ectoendoparasiticides can cause risk of health hazard to milk consumers of such treated cows as the drug is bound to protein and adipose tissues leading to its delayed excretion. The ivermectin residues upto the level of even 60% in bulk milk have been studied by
Hanan et al., (2016) in Egypt.
Kochetkov et al., (2017) studied determination of Fenbendazole in milk by Liquid Chromatography and found the concentration of Fenbendazole versus time after treatment.The European Medicines Agency (EMA) in 2011 published a report on the use of Panacur, a liquid suspension of fenbendazole and the results warned that excessive use of panacur may cause anthelmintic resistance.
