Larvae with European foulbrood, showing yellow stripes that increase and become brown as soon as the larval tissue is destroyed. This appearance continues until the larva’s death.
Infectious-contagious disease affecting bees’ rearing in a few days, two or three days. It is characterized by producing morbid processes in the midgut, ventricle and causes the death of larvae before reaching nymphs.
The etiology of this disease is not simple, because it presents several bacterial microorganisms that act independently or jointly, according to the circumstances. These agents are: Melissococus pluton, Melissococus alvei, Acromobacter euridyce, Streptococcus faecalis, Bacillus laterosporus and Bacillus morpheus.
Nevertheless, some authors consider three different diseases, depending on the etiological agent:
– European foulbrood, caused by Melissococus pluton.
– Benign loquat, produced by Bacillus alvei, Bacillus laterosporus, Bacillus gracilesporus and Bacillus apidarium.
– Breeding acre – whose agent is Streptococcus apis.
The true agent causing the disease is Melissococus pluton, as it is the first bacterium to be determined, while the other agents are secondary invaders. This bacterium is resistant to the acidity of the royal jelly (ph = 3,4), in which other bacteria can not develop. When the larvae are larger and begin to feed on different potatoes (which are usually less acidic), the secondary invaders appear.
Melissococus pluton is a lanceolate coconut, 0.6x1mm in diameter, first observed in 1912 by White, with cells of varied size (a micron or something larger), appear in chains or forming small colonies with different longitude. The bacteriological test is positive. It does not form resistance elements (spores). It boosts glucose and fructose, being the variable result for maltose and salicin. Does not use citrate. It grows in basic culture media, requiring the presence of lysine, cysteine, peptone or yeast extract. It grows best under microaerophilic or anaerobic conditions. It has remarkable endogenous resistance: one year for dissection, 20 hours for direct exposure to sunlight and 25 days for putrefaction at room temperature.
The infection of the larva takes place orally, when it ingests the food that is contaminated by the causative agent, M. pluton, that, when arriving at the mesointestino, installs itself in the peritrófica membrane and reproduces quickly, accumulating in the surface of contact with the intestinal light and later invades the rest of the structures of the larva, causing the death and turning it into a mass of yellowish brown color, when the cello is open.
Due to the resistance of M. pluton to the high acidity of the royal jelly, its action is effective during the initial days of the larval phase, joining the low oxygen tension in the digestive tract at these moments. This high acidity seems to exert a bactericidal action on B. alvei and S. apis, which does not reproduce in larvae fed with royal jelly.
Symptomatology is variable. The larvae lose their milky white and shiny color. They become yellow and opaque, showing transparently the tracheal system. When lifted with a transfer needle, they are flaccid (neither viscous nor filamentous). As the larvae die, they are withdrawn from the empty cell. The larvae developed alongside the eggs are observed, the honeycomb presenting a mosaic of ages, as it is known as the sauteed brood.
At no time is there any adherence of the larval remains to the dead walls of the cello, and simple extraction is easy, so that the comb is struck and the scales fall. When the infection is severe, the workers can not remove all the dead larvae and find them in the cells with a dark color, close to the brown, and may feel a rotten odor. The larvae die when the cells are operculated, presenting a color similar to that of the American Loque.
Young larvae under 2 days old are infected when they consume food contaminated with bacteria. These spores germinate rapidly and multiply in the intestine, leading to the death of the larvae. Cleaning bees that try to remove the larval debris, contaminate themselves with microorganisms and pass them to the nursing mothers during the exchange of food. The latter transfer the larvae during their feeding. The death of the larvae can be accelerated by the action of the secondary bacteria.
Dissemination of the European Loque
The propagation of these bacteria takes place through the bees themselves (bees cleaners and looking for swarms that have contaminated bees), by means of old combs that present scales, contaminated larvae and pollen. One of the factors preponderant to trespassing to other hives is the drift and multiplication of diseased colonies.
Stress (humid and cold environments favor the development of the disease), the presence of Nosema apis, poor nutrition, poor handling and biological imbalances are some of the agents that predispose the disease.
European foulbrood usually disappears due to the cleaning capacity of some hives, although the most common is the persistence of dangers, compromising the viability of the colony. Programs aimed at obtaining bees with higher cleaning behavior may greatly reduce the presence of European foulbrood.
Nuclei may be more susceptible to disease than strong colonies, so it is always a question of multiplying healthy colonies, even though the queens with which the nucleus heads are resistant. Nuclei made from diseased colonies may die before the new queen expresses its genotype.
There is no medical prophylaxis for European foulbrood. Preventive treatments are not advisable, and only after diagnosing the disease should all colonies be treated without exception. The introduction of swarms acquired outside the holding must be quarantined and searched to avoid the incidence of the disease. A poorly fed colony is very likely to contract European foulbrood. Foods of unknown origin shall not be used.
For handling we must bear in mind that it is very damaging to carry out the opening of the hives in cold or rainy weather. The cooling of the larval population brings with it the death of this and the predisposition to contract the disease. It is necessary to systematically disinfect all the material of exploitation, through procedures that will depend on the nature of the material to be disinfected. If the disease is very developed (occupies a large part of the calf), the most advisable is the destruction of the colony, and can use the material soon after a good disinfection.
To combat this disease, it is recommended:
– Do not buy or use queens of dubious origin, they may be sick or old.
– Use young queens of good origin.
– Do not use old combs or dubious material.
– Have clean water available for the bees.
– Have a good winter.
It is important to have a good balance between nurses and workers and a good diet. Autumn and spring are the most favorable times for the development of the disease. If colonies do not dampen their populations during spring growth, it is advisable to encourage colonies with sugar syrup before resorting to chemical control. This practice can solve the problem and increase the breeding area.
It is a bacterium called Melissococus pluton.
– Make saute.
– Open creature, few blown and torn operculums.
– Rotten odor.
– Larvae coiled on the bottom of the cello or twisted on the side walls, with irregularity.
– Soft dead, aqueous, occasionally sticky larvae, not less than 2,5 cm.
– Scales coiled on the bottom of the cello in an irregular, soft, easily extracted form.
– Inside the colony: bees cleaners, nurseries, honey, pollen, moth larvae.
– Between colonies: pillage, drift, artificial feeding with honey, manipulation, transhumance, nuclei.
– Do not use preventive treatments
– Very affected hives: Incineration.
The diseased larvae turn slightly yellow. As the decomposition progresses they become coffee-colored and lengthening the length of the cell. When moving with a toothpick the viscous mass can form a wire up to 30mm. There is a smell of putrefaction.
The creation aspect looks like a pepper pot. When they dry the affected larvae turn dark brown and form a scale near the bottom wall of the cell. Good lighting is essential to observe the changes. The wax seals when present are drilled or sunken with a soaked appearance.
The affected larvae turn yellow and the trachea is visible in the open cells. Young unsealed larvae (3 to 5 days) in the form of a “C” around the walls of the cell.
The creation aspect looks like a pepper pot. The dead larvae are found behind the concave and perforated wax of the cells. The viscous mass inside the cell is less sticky than in American foulbrood. Sometimes it can also smell putrefaction.
American foulbrood and European foulbrood are not the same, but they can sometimes cause confusion, as well as other diseases that affect the breeding of bees.
The larvae contaminated with European foulbrood do not appear white, have a dark brown color and are alternated in different positions in the cell.