Lumpy skin disease (LSD) is a vector-borne disease of cattle caused by lumpy skin disease virus (LSDV) which belongs to genus Capripoxvirus [1, 2]. Clinically, the disease can manifest in a wide spectrum ranging from severe acute to sub-acute and in-apparent forms. Typical signs observed are fever, enlargement of lymph nodes, nasal discharge, and firm skin nodules . The control of LSD is mainly based on mass vaccination of the susceptible cattle population with live attenuated capripoxvirus vaccine [4, 5].
Recent studies suggest that LSDV vaccination stimulates equally cell mediated and humoral immunity [6,7,8]. The humoral immune response is of paramount practical importance to obtain information on the immune status of animals post infection or vaccination. The detection of antibodies against LSDV is possible starting one to 2 weeks post vaccination, increases gradually until 35 days to 12 weeks post vaccination, and is described to last until 40 weeks post vaccination [6,7,8]. Standard serological methods like virus neutralization test (VNT), agar gel immunodiffusion, indirect fluorescence antibody test (IFAT) and Western blot are described [9, 10].
These tests are expensive and time consuming therefore limiting their use for fast serological screening of cattle populations. The only test validated to date by the OIE is the VNT, coming along with high specificity and good sensitivity, but reduced high-throughput application. As performing VNT includes the handling of live capripoxvirus, its application can face additional restrictions . The IFAT comes along with the disadvantage of increased cross reactivity with bovine papular stomatitis virus and other poxvirus antibodies.
For efficient immunological investigations at large scale, Enzyme-linked Immunosorbent Assay (ELISA) has been found to be more suitable compared to the above-mentioned serological methods. Few studies on the development of ELISA tests for LSD-specific antibody detection by using recombinant P32 , recombinant two virion core protein of sheeppox virus , and inactivated sheeppox virus as coating antigen for antibody detection  have been published. A double antigen ELISA from the IDvet® is currently the only commercially available kit for detection of capripox specific antibodies applied in field studies for seromonitoring . All of these ELISA have been developed for plasma or serum as sample matrix to be used.
Apart from blood, the detection of specific antibodies is also possible from other matrices such as milk. Cow milk contains three major classes of immunoglobulin’s (Ig): IgG, IgM and IgA . Dominant class of immunoglobulins in milk, comprising about 65% of the total, is IgG. The concentration of IgG varies between serum and mammary secretions. Highest concentrations can be found in colostrum (32–212 mg/ml), followed by serum (25.0 mg/ml) and finally in milk with about 0.72 mg/ml . As for the colostrum, a steady gradual decrease of antibody levels is described each hour . The concentration of antibodies in regular milk is much lower than that in colostrum and depends on factors like clinical or subclinical mastitis, age, breed, feeding system and the stage of lactation. In addition, primiparous cows are described to have colostrum and milk with overall lower levels of immunoglobulins compared to multiparous cows [18, 19].
Using milk for the detection of antibodies by ELISA has been found suitable targeting antibodies against viruses such as bovine viral diarrhea virus (BVDV) , bluetongue virus [21, 22] and bovine alpha herpesvirus 1 (BHV-1) . As milk samples are non-invasive and cheaper to collect compared to serum and plasma, this method has been widely used in mass screening activities targeting either individual animals or bulk milk samples for the determination of the immunological status at animal or herd level respectively.
In this study, we investigated the suitability of milk, as individual animal and bulk sample to detect LSD-specific antibodies using a commercially available capripox ELISA designed for serum and plasma samples.