Moderhinke is a highly contagious and painful hoof disease in small ruminants. It is characterised by inflammatory changes in the hoof area and the resulting lameness of the supporting legs. Moderhink is associated with considerable economic damage in sheep farming. The primary causative agent is the gram-negative anaerobic bacterium Dichelobacter nodosus(D. nodosus), which occurs in benign or virulent variants. Only the virulent variant of the bacterium leads to the full expression of the moldy limp. The mildew is highly contagious and thus leads to a particularly rapid spread within the herd. On contaminated pastures, the pathogen spreads to more and more animals through indirect transmission via the soil. Even apparently healthy animals can transmit D. nodosus. Infection can also occur via contaminated transport vehicles or drove paths. Apart from the virulence of the pathogenic strains involved, humidity, temperatures above 10 °C, inadequate hoof care, hoof lesions and the secondary infections mentioned above are decisive for the infection and the resulting clinical manifestation. It is possible for the pathogen to spread to uninfected farms. The pathogen Dichelobacter nodosus has a limited life span of about 14 days on pastures and in the soil. It survives only briefly in dry environments, so that a risk of infection can be ruled out after only a few days. On moist soils, however, the bacterium can survive for up to 42 days, and even up to 6 months under favourable conditions. In hoof horn and in diseased hooves, the pathogen can be detected for up to 3.5 years.
There are different stages of the disease. The extent of the lesions is divided into the grades 1-5 by the definition of the stages of fart disease. In principle, all forms of the disease can occur simultaneously in one foci:
|0||Hoof gap without changes, hairy|
|1||Inflammation of the skin in the hoof gap, redness|
|2||greasy, smelly deposits in the hoof gap||3-4 days|
|3||Detachment of bale horn and inner wall|
|4||Extension to entire sole and outer wall|| |
|5||Extension to the tip, shoeing out||> 21 days|
Definition of the Moderhink stages according to H. Strobel 2018 The initial stages are indistinguishable from simple inflammation of the cleft without involvement of D. nodosus. Beginning with inflammation in the interclaw cleft, dermatitis interdigitalis, there is progressive inflammation and damage to the claw horn. The horn is detached from the claw corium to varying degrees; there is often a foul-smelling, grayish-white greasy mass between the two as a product of the suppurative process. Severe cases are characterized by sole perforations and sloughing. Typical symptoms include lameness ("support leg lameness") and kneeling to feed on the forelimbs to relieve the painful claws. Affected animals lie down more and as a result there is reduced feed intake, emaciation, wool damage and performance depression.
Moderhinke is a painful disease and must be treated with regard to animal welfare. Measures are necessary both in the case of benign infection and in the case of virulent infection of D. nodosus, as acute pain associated with reduced performance also occurs in the benign form. With regard to therapy, decisive changes have resulted, among other things, from the new approval of drugs.
- Separation of healthy and diseased animals
- Surgical treatments such as the complete removal of the affected altered hoof horn and the purulent mass by cutting are problematic due to the lengthy recovery process and the painfulness. In principle, bleeding injuries should be avoided during hoof trimming. Dressings should be changed daily because of the ideal warm, moist, anaerobic microclimate (promotes bacterial growth!). Safe disposal of necrotic waste after surgical treatments is necessary due to the risk of infection from bacterially contaminated wound waste!
- Treatment of the affected hooves with antiseptic wound spray and/or hoof baths (e.g. with zinc sulphate).
- Antibiotic general treatment of severely diseased animals
- Follow-up control and treatment at regular intervals until cured
- Vaccination works both prophylactically and therapeutically. Vaccination alone is not sufficient to cure the herd.
Moderhink is a herd disease. The exclusive treatment of individual diseased animals is therefore not sufficient. Herd sanitation is necessary for successful control of the moldy mildew disease. To achieve success in herd sanitation, the following criteria must be met:
- All animals must be included in the treatment
- All acute hoof infections must be treated within the first few days.
- All treated animals must be followed up until complete recovery.
- All healthy animals must be protected as soon as acute cases occur.
Individual animals should show marked improvement in lameness symptoms within a few days after treatment. Complete healing usually takes as much time as the course of the disease before therapy. In the herd, it is necessary to examine and treat all animals at the same time: Infected animals are systematically treated with antibiotics; healthy animals are protected by precautionary measures (hoof baths). By different colour markings and/or local separation of healthy and diseased animals it is possible to observe the further course of the disease in the herd. Regular herd treatments can lead to freedom from the disease if the number of latently infected animals can be continuously reduced over a period of years. After recovery, animals must be moved to pasture that has not been used for at least six months to prevent reinfection of irritated hooves. However, if animals in a herd are in contact with the wild animal population, this is difficult to achieve.
The application of molecular biological methods not only allows the rapid processing of a sample and the typing of the specific fattening pathogen Dichelobacter nodosus, but also the detection of subclinically infected animals, which is of great importance for herd control. PCR examination of swab samples of the interclaw cleft can be used to determine whether infection with the benign or virulent form of D. nod osus is present. In routine diagnosis, no cultivation of the pathogen is usually necessary if the picture is clear. Microscopically, the rod-shaped bacteria of Dichelobacter nodosus can be visualized by Gram stain. Differential diagnostic considerations include:
- traumatic lameness syndromes (e.g. wall, sole, tip abscesses, foreign body injuries, haematomas)
- inflammation of the cleft(dermatitis interdigitalis)
- atypical claw inflammations (e.g. CODD (contagious ovine digital dermatitis), the podal form of labial bursitis or infections caused by Prevotella sp. and Fusobacterium necrophorum)
- Panaritium (foot abscess, "heat foot")
- Foot-and-mouth disease
- Plastic swab samples of the interclaw cleft (without medium).