Interdigital phlegmon in dairy cows: focusing on some clinical aspects that can target the therapy

Introduction
Interdigital phlegmon (IP) is a severe, infectious necrotic inflammation of interdigital subcutaneous tissues. Necrotic lesions rapidly extend to the skin, corium and deep structures if therapy is not promptly established. It’s a sporadic infection sometime characterized by epidemic outbreaks causing significant economic losses. IP is caused by Fusobacterium necrophorum in synergy with Dichelobacter nodosus. Trueperella pyogenes, Prevotella spp, Porphyromonas spp, Bacteroides melaninogenicus can also be involved. The aim of our study was to review the records of IP cases in order to analyze its prevalence, complications, treatment and results. 

Materials and Methods
The medical records of dairy cows submitted to functional and/or therapeutical trimming during 2016 were reviewed. We obtained information on: overall number of digital lesions, no.of IP , number of complications, management and follow-up. 

Results
From January to December 2016, 6177 cows were routinely trimmed in 41 dairy farms of northern Italy. In 23 farms out 41 (63 %) 154 cows were diagnosed with IP (2,5 %) for a total number 162 IP cases: 66 acute, 50 subacute, 46 chronic. In 46 cases (28,4 %) the infection involved the pododerm; deep structures were involved in 5 cases (3,1%): distal phalanx in one case and distal joint in 4. The outer digit was affected in 40 cases (24,7%), inner digit in 10 (6,2 %), both digits in one case. The digit was’nt reported in the remaining cases. Eighty cows out 154 (51,9 %) were submitted for systemic antibiotic therapy. Horn and necrotic corium debridement was performed in complicated cases. Eighteen cases (11,1 %) were bandaged, in 25 cases (15,4 %) a block was applied and in 20 (12,3 %) were applied both. Two cows with septic arthritis were slaughtered, one had the amputation, one just systemic therapy. Follow-up was available for 45/162 cases (27,8 %): 15/45 (33,3 %) healed; 1 relapsed (2,2%); 1 developed chronic septic arthritis (2,2%). Twentyeight (62,2 %) had after-effects: 14 interdigital ulcerations, 10 septic chronic pododermatitis, 4 chronic swelling. 

Conclusions
Because IP frequently involves the surrounding tissues (28 % of cases) and deep structures (2,5%), and mainly of a single digit, diagnosis must be timely to prevent these complications. The foot should be carefully examined to identify the affected tissues, corium, phalanxes, joints, whose involvement can dictate the most appropriate and cost-effective therapy. Blocks, bandages and systemic antibiotic therapy, are of major importance to promote healing.