Case reportAntimicrobial photodynamic therapy for caseous lymphadenitis abscesses in sheep: Report of ten cases
Introduction
Caseous lymphadenitis abscesses (CLA) is a chronic infectious disease, reported as one of the major diseases that affects small ruminants herds around the world. The main cause for the cosmopolitan character of the disease is the global commercialization of infected animals associated with a faulty sanitation program [1].
Corynebacterium pseudoturberculosis is considered the main causative agent of CLA pathogenesis, nevertheless, other bacteria were also correlated as aetiological agents. The high prevalence of CLA represents some risks for the herd, such as the reduction of fertility, delayed development, gradual weight loss, occasional death of animals and condemnation of carcasses at the slaughterhouse [1].
The worldwide accepted diagnosis is the clinical identification of the abscesses in superficial lymph nodes that can be found in several animals of a same herd. The most affected lymph nodes mandibular, parotid, popliteal, subiliac, superficial cervical, mammary and retropharyngeal. More rarely, internal lymph nodes from visceral organs can also be affected, leading to systemic changes and progressive weight loss [1].
The usual therapeutics consists in surgical drainage followed by systemic antibiotics, associated or not with local antiseptics solutions over the opened lesions [2], [3]. However, the treatment period is long and, until now, there is no proven successful treatment available.
In this context, antimicrobial photodynamic therapy (APDT) could be an alternative approach for CLA. In fact, due to antimicrobial resistance worldwide, APDT has been used in the treatment of topical infections. Its action results from the interaction of a photosensitizer (PS), visible light and molecular oxygen. In the presence of oxygen, the activated PS can react with neighboring molecules by electron transfer, leading to the production of reactive oxygen species (type I reaction) or by energy transfer to oxygen, resulting in the production of singlet oxygen (type II reaction). Because PS accumulates in cell targets, only irradiated cells are impaired. APDT also takes advantage of its action on multiple targets not promoting microorganism resistance. Several strains of gram-positive and negative bacteria, fungi, protozoa, viruses and pathogenic algae were shown to be susceptible to the APDT [4], [5].
Methylene blue (MB) is a PS commonly used in APDT associated to a red light to treat topical infections of different etiologies [5]. Thus, in this study, we investigated the feasibility of MB-mediated APDT to treat CLA in sheep after surgical drainage.
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Case report
For this study, we used ten crossbreed sheep, adults, male and female, from the same herd, presenting lymph nodes enlargement characteristic of CLA. Inclusion criteria were the presence of a subcutaneous swelling in the lymph nodes, followed by external palpation to identify the consistency of the subcutis and presence of purulent exudate.
After the clinical diagnosis, we performed the surgical drainage. The sheep had their abscess fur removed by a shaver, and the skin was cleaned with alcoholic
Discussion
Diseases caused by multidrug-resistant microorganisms are emerging in veterinary medicine due to the overuse of antibiotics, particularly in food animals. Thus, alternatives to conventional treatments must be developed.
In our study, APDT showed to be a suitable alternative approach for CLA as it presented a faster time of healing as much as no recurrence during six months of follow-up. This finding is awfully attractive since different results were observed by other authors, who reported a
References (6)
- et al.
Corynebacterium pseudotuberculosis and its role in ovine caseous lymphadenitis
J. Comp. Pathol.
(2007) - et al.
Methylene blue in photodynamic therapy: from basic mechanisms to clinical applications
Photodiagnosis Photodyn. Ther.
(2005) - et al.
Comparative study between photodynamic and antibiotic therapies for treatment of footpad dermatitis (bumblefoot) in Magellanic penguins (Spheniscus magellanicus)
Photodiagnosis Photodyn. Ther.
(2015)