American foulbrood is a bacterial disease produced by the bacillus Paenibacillus larvae (White, 1906) a flagellate mobile microorganism, which is in the form of a rod about 2.5 to 5 microns wide by 0.4 to 0.8 micros . A key feature of P. larvae is the formation of endospores, extremely resistant to heat (30 minutes at 100º and 15 minutes at 120º), chemical disinfectants, chlorine, UV radiation (20 minutes), iodized and hot water with any additive.
The spores of Paenibacillus larvae can remain infected for more than 40 years, although their visibility is diminished soon in this period. They present the fundamental physical peculiarity of having Brownian motion, that is, when observed under the optical microscope, they move constantly, thus allowing a better identification.
Symptomatology and damages
American foulbrood is a disease of the baby that kills it as soon as it finishes its stage as a larva. They die mainly in a pre-pupal state, even though some are likely to do so in a pupal state. One month after the larva’s death, a scaling is characteristic of the lower wall of the cell, which can remain in the combs for several years without being removed by the bees.
When the disease arises, the earlobes of the baby’s comb become moister and darker, to fuse. It is at this moment that the bees begin to remove the remains of the larva.Qué died, the young become a brown color and expel an unpleasant odor.
The larvae killed by American Loque acquire a semifluid consistency, which resembles a chewing gum, which is why when a toothpick is inserted inside the operculum it drags a brown residue in the form of a viscous herb, which extends up to 4 cm. Currently, several cases have been presented that demonstrate a clinically dubious symptomatology (Loque atípica). Laboratory techniques confirm the presence of Paenibacillus larvae, the causative agent of American foulbrood. In these cases, different bacteria are involved.
The larvae of bees are infected by eating the food contaminated with American Loque spores, which germinate irregularly in a period between 24 to 48 hours in the intestine and give rise to vegetative cells (bacilli). Bacteria can cross the intestinal wall until the larvae become pre-pupae. When this happens, the bacteria reach the hemolymph and proliferate, multiplying violently until killing the baby.
A scale has approximately 2.5 billion spores. Larvae under 24 hours only need 6 spores to infect, while a 3-day larva needs to ingest millions of spores to be infected; after this period they are hardly susceptible. The larvae of queens are more susceptible to diseases than the larvae of workers and these are the larvae of drones.
The main agents for spreading the disease are: pillage, bee drift, feeding (honey and pollen), exchange of bee keeping from one beehive to another and beekeeper handling (scraper, gloves, abandoned combs, contaminated vehicles, etc.).
The colonies very affected by American Loque have gradually reduced their population to the point where the queen, with few bees, abandons the same, although the causes of this abandonment are not yet well known. Some authors maintain that it is due to the excessive odor in the environment of the hive. This feat leaves the infected hive exposed to the plunder of other colonies of the apiary.
American foulbrood is a non-seasonal disease, which invariably leads to colony loss. It can happen that when an outbreak appears, this soon disappears, it is unlikely that the bees can remove from this colony all the spores formed during the first infection. Therefore, at some point these spores can start the cycle again.
Spores can be transmitted to larvae by adult bees in charge of cleaning the combs; there may also be contamination by spores that persist in the bottom of the cells.
Adult bees can identify the infection very shortly after it occurs. During the embryo at the time of electing a new beehive, they can not distinguish between contaminated and non-contaminated combs, so keeping dead and abandoned hives in the field can lead to swarming.
In most cases, recovering diseased colonies seem to heal abruptly during the honey season. This is primarily due to: Spores can be diluted in freshly harvested nectar to the point where susceptible young larvae are unlikely to receive them with food.
The bees avoid storing honey or pollen in locations that contain remains of larvae killed by American foulbrood. The fluid of the nectar stimulates the hygienic behavior of the nursing mothers.
Some pupae infected with American foulbrood die after the tongue has formed. The infected pupa begins to decompose and shrinks, but the tongue remains pointed up almost touching the wall.
Importance of honey as a source of contagion
Presence of spores in honey: 100% of the infected colonies, 26.1% of the healthy colonies located in apiaries that have a positive case, 4% of healthy colonies of apiaries that do not present the disease, but located in infected areas.
Maintaining low levels of infection contributes to the slowing down of the disease and its degree of diffusion, since during the drifting process the bees of the infected hives are able to transmit the disease to strong hives.
The phosphorus test – an excellent way to test American foulbrood.
Because it is an aggressive disease, it is important to recognize it and detect it in the first moments of the infection. Certain guidelines should be considered at the time of inspection: Percentage of inspected breeding stock. The location of the breeding chamber of the frames being inspected. Frequency of the year / season in which the inspections are carried out. Close observation of opercula and larval remains. Time spent on inspection of the breeding chamber. During observation, the naked eye can be seen: The baby’s comb does not have an even posture. You see the empty cells, without posture, nor larvae, alternated with sprigs.
In the comb’s combs can be found fused, darker than normal, greasy and with small perforations. The dead grubs of brown color, of “gummy” aspect, that when introducing a toothpick and when removing it, this one brings a paste type bubble gum. The scales, the product of the dead larvae, are adhered longitudinally to the wall of the cells. They are very dark brown, almost black, very difficult to remove. The dead larvae begin to decompose, exuding a characteristic strong odor.
It is necessary to make a differential diagnosis with European foulbrood. Due to the characteristics of the disease itself, since LA is detected in a region, it can hardly be eradicated completely in the same. Any of the methods described below must be complemented imperatively by an intensive program of periodic reviews of apiaries (at least 90 days apart), including the winter season, since a single colony abandoned in the field can destroy the work of several years of control.
It is essential to adapt the actions tending to control the disease according to each case and to each particular system, duly assured by a technician.
Destruction by fire of diseased colonies
This is always the best option to eradicate the disease. The destruction implies: A well should be made in the earth with a diameter according to the amount of material to be burned, of approximately 60-70 cm of depth. On the eye are placed 2 or 3 green sticks or metal bars, where the material to be burned will be placed.
Kill the bees by using an insecticide or cloth soaked in naphtha (300ml). For this procedure humus should not be used, since the bees fill their papes with contaminated honey increasing the risk of escape and contamination of other hives. This procedure can be performed at any time of the day due to the fact that the bees that are working hardly have spores in their chats, since they return with nectar freshly harvested from the flowers.
Once the bees are found to be dead, the combs, bees and pictures are burned. If the wood material is not incinerated together with the bees, it should be disinfected or sterilized perfectly.
During the firing process, honey should be prevented from spilling out of the well. Once the incineration is complete, the well must be capped to prevent the plundering of honey, wax and propolis, which have not finished burning. This system is recommended when the incidence of American Loque in apiaries is less than 5% per year.
Cells punctured in a comb infected with American foulbrood.
Box technology is one of the most effective methods to recover colonies affected with Paenibacillus larvae. Although this technology is not 100% effective, it allows to diminish the infection better than any other alternative of handling.
The following steps are as follows: Cut the wings and cage the queens of the affected hives.
Shake with a funnel and a water spray; place the bees inside a package, note that the bees must be sprayed in advance. To burn a colony we must avoid the use of humus, replacing it with a good sugar water spray.
The amount of bees required for confection of a colony recovery package is approximately 1800 grams, which are about 6 frames of bees.
If a colony very weakened by an illness does not reach this weight, it must be completed with bees from another hive.
Kill the surplus of bees and incinerate the honeycombs and pollen. Honey can be extracted if handled properly to prevent looting. The rest of the beekeeping material should be disinfected.
Place the feeder packages in a dark, cool place for 48 or 72 hours. To prepare a breeding chamber, with three pictures of stamped wax and a feeder, never be used tables with worked wax, since the bees tend to put the honey with spores in the cells.
Place the package inside the chamber; during the operation the queen should be removed and placed between the stamped wax tables, removing the sugar buffer; keep the chamber completely airtight for 48 hours.
Open the hole a little and refill the syrup feeder with antibiotic. Feed every 4 or 5 days, until they complete the chamber.
The procedure consists of: Shifting the hive from its place and placing an empty core and frames. Shake the bees frames inside the feeder core.
The frames of the hive with rearing must be imperfectly INCINERATED and the chamber disinfected. Frames with wax may be fused and used to make stamped wax again. The honey can be extracted and used only for human consumption, “you should never feed the bees with this honey”.
The nucleus, in which the bees will have been shaken, will be left in place until dusk to ensure that all bees return from the field; at that moment, it should be closed with a metallic screen that allows the aeration, leaving closed for 48 or 72 hours.
At the end of that time, the core can be transferred to a chamber with stamped wax and a feeder. Feed every 4 or 5 days, until they complete the chamber. Once the bees have worked and the first worker larvae are present, the feeder should be added with the syrup and the antibiotic. This technique is simpler than that of the package, and offers much less results, and there may be a recurrence of American foulbrood, such as loss of hives during the process. In most cases, bees die in the nucleus or leave the chamber.
In diseased pupae, parts of the body mostly lose their characteristic shape, even though the tongue remains right and prominent.
Immediately place a disinfected chamber next to the sick hive. Put 3 pictures of stamped wax, a feeder and a queen. It is important to know that this methodology only lowers the level of infection of the hives, it does not eliminate the disease completely, and it is highly probable that it will reappear in the coming months. This method is advisable only when the number of hives affected is very large and the level of disinfection of each hive is low.
Disinfection of beekeeping materials
Sterilization by fire: in case of not burning the chambers, floors and ceilings, an exhaustive disinfection should be carried out, which may consist of:
Burned in the shape of a pyre or chimney: 6 or 7 inverted loops are placed in the form of a chimney. These are sprayed with kerosene, underneath is placed a ceiling or floor with a little kerosene. Once everything is ready, set the fire, always keeping in mind that all the materials used are flammable and allowed to burn until the beekeeper notices that black smoke, typical of the burning of the wood, begins to appear. At that moment, a ceiling is placed on the pile of handles in order to drown the fire. If it does not go out, it is advisable to knock the battery out and dry it with sand or water. Floors and ceilings can be burned individually with kerosene, one by one. As soon as the producer performs this procedure several times he will return to do it efficiently that a lot of material can be disinfected in a short time.
Hot Paraffin: This system consists of submerging the apical material in paraffin at 150º. For the respective process, it is necessary to build some devices that allow the work to be carried out safely.
Wash with caustic soda: Submerge the material in 15% caustic soda with boiling water, this must be done with great care since the product is highly corrosive and can damage the beekeeper. Before treating the materials, they should be scraped so as not to waste the solution dissolving large pieces of wax and propolis and thus facilitate penetration into the cavities of the materials. The material should remain submerged for a maximum of 5 to 20 minutes as the solution destroys the wood fibers. Once removed, it should be put in clean water. It should be noted that sodium hydroxide is extremely toxic.
Final considerations about honeycomb sterilization
No doubt the best process of sterilization is to burn the combs containing larva residues with American Loque and to fuse all those that do not contain cria, for their subsequent stamping, since in this process large amount of spores are destroyed or are eliminated.
Many of the products mentioned here are dangerous to health and the environment, so it is recommended to: Acquire products of recognized quality. Read the instructions carefully. Strengthen precautionary measures as many of them are caustic. If in doubt, consult a professional or a specialized center.