New Aspects of Mortellaro’s Disease: A Literature Review
Authors: Korukina M. V. 
Published: October 2024

Introduction. All over the word, hoof diseases, and Mortellaro’s disease in particular, are being among the most widespread and difficult to treat diseases in dairy cattle husbandry. They cause irreparable economic damage to the dairy industry by reducing the cattle reproductive ability indicators, feed conversion ratio, which compels to spend considerable amounts on treatment, prevention and culling of animals. Mortellaro’s disease is especially widespread in Europe and Western countries, but the current rate of national economy growth leads to the necessity to purchase the cattle abroad, which results in the increase of the Mortellaro’s disease incidence in Russia: at the farms where cattle has been imported, the percentage of the disease is 14.17±5.15% of the total number of hoof diseases in the herd. The aim of this review is to summarise the results of scientific research on the Mortellaro’s disease pathogenesis over the past 20 years.

Materials and Methods. To achieve the stated objective, the criteria of inclusion into the search were defined. It was decided to include in the review the studies/reports presenting the results on: 1) the disease etiology and factors affecting the course of Mortellaro’s disease; 2) symptoms of Mortellaro’s disease manifestation in different species of farm animals; 3) the methods of Mortellaro’s disease treatment. The materials published in Elsevier, ASM Journal, Irish Veterinary Journal, Thieme, American Dairy Science Association, Epidemics, Schweiz Arch Tierheilkd, Journal of Clinical Microbiology, eLIBRARY.RU, Google Scholar have been investigated in the frame of the literature search. The search by the following keywords was done: interdigital dermatitis, Mortellaro’s disease, hoof diseases of cattle, contagious interdigital dermatitis. The time range of sources – those published within the period from 2003 to 2023.

Results. In total, 44 articles have been analysed, 33 of which have been included in the present review. According to the studied materials, one of the prerequisites underlying the spread of Mortellaro’s disease in the Russian Federation is the import of the infected cattle, since the measures undertaken during the temporary housing and quarantine periods do not give the desired result. The animals get infected with the bacteria of the genus Treponema, which are localized deep in the hoof tissues, therefore, after the disease is endured, it turns into its chronic form. The specific symptoms of Mortellaro’s disease course in various cattle breeds have been established: in beef cows and buffaloes the interdigital dermatitis is characterised by a low level of pain symptom severity; in sheep – by the ulcerative lesions of the сoronary band, which progress and lead to the destruction of the abaxial hoof wall and loss of the hoof horn. The areas with the erosion are very painful, but the intercellular adhesive junctions are not lost, which allows for positive prognosis of the disease. The main indicators of productivity and fertility are reduced due to the disease, as is the immunity in general, and there is an estrous cycle delay. In the samples of patients sick with the digital dermatitis, an increase of the number of intact and degranulated mast cells is observed, compared to the healthy ones, which indicates that mast cells can play an important role in the pathogenesis of digital dermatitis. Nowadays, the Mortellaro’s disease treatment abroad and in Russia is based on the elimination of symptoms, and not the pathogen itself. The local treatment is mainly represented by the antiseptic baths, surgical treatment, local application of antibiotics to the wound. The experiments on antibiotic susceptibility of Treponema, which are the important step in the search for the specific treatment of Mortellaro’s disease, have been performed. The antibiotic susceptibility tests gave positive results (all isolates of Treponema were sensitive to tiamulin, valnemulin, tylosin, aivlosin, lincomycin, doxyclin), however, the difficulty lies in the method of drug administration into the source of Treponema localization, since the conventional ways of administration of antibiotics entail restrictions on the sale of milk and meat.

Conclusion. The presented review of the scientific publications on Mortellaro’s disease made it possible to summarise the currently known results and identify the areas for further research. For example, it should be still investigated why the interdigital dermatitis requires the presence of many Treponema species rather than one? What role do representatives of the Mycoplasma, Porphyromonas and other bacteria play in the pathogenesis of the studied disease? And of course, there is a serious scientific gap in finding treatment of Mortellaro’s disease capable of eliminating the pathogen itself, rather than its symptoms. It should be mentioned that not all Treponema species can be cultivated, which also slows down the scientific process and makes the problem of Mortellaro’s disease treatment relevant worldwide.