OLIPHANT F. JACKSON, Ph.D., M.R.C.V.S.
Using a simple technique it has been possible to show that in the dust from a bale of hay or straw there are not only mould spores but pollen grains, living forage and dust mites, their eggs, nymphs and faecal pellets. The fact that these cause diseases in man and animals is issued as a warning. These findings make it even more important that neither hay nor straw be used in tortoise hibernation boxes.
For several years now I have been advising BCG members not to use either hay or straw as insulating material for tortoise hibernation boxes. I have demonstrated the clouds of dust that emerge when old hay or straw is shaken out.
This is to give information of some of the living things that can be found when dust from hay and straw samples are examined under the microscope.
Tortoises are not the only species of animal known to get diseases of the respiratory tract from contact with moulds and other airborne contaminants. Overt chronic pulmonary disease in horses has been associated with mouldy feeds, mouldy bedding materials, poorly ventilated stables and previous respiratory disease (Clarke 1987). A condition known as 'farmers lung' is a hypersensitive pneumonitis that occurs in farm workers who have to open up bales for livestock in the winter months and are exposed to moulds fro m either hay or straw.
Methods used in the microscopic examination of the dust from hay A clean microscope slide had the upper surface wetted. It was then placed on a sheet of clean paper and the hay or straw sample was shaken over it from a height of eighteen inches. When the slide had become covered with plant tissue the shaking was stopped, the excess plant material was lifted off and the slide taken to the laboratory. A few drops of water were added to the surface and a cover slip lowered on top. It was then transferred to the microscope stage and examined.
Other samples were stained using a mountant containing 5g gelatin, 4g phenol, 40ml glycerine, 1 55ml water and 0.01 % safranin as described by Clarke and Madelin (1987). This staining was necessary to show up the spores.
Results under the microscope
Under the low power objective giving a x 100 magnification a wide variety of plants, pollen, organisms and arachnid mites were seen in fresh unstained material. The following were identified:- fragments of plant tissue, plant hairs, the occasional pollen grain, and live dust and forage mites of six different species (Fig. 1 ), some with fat multiple jointed legs, some with long body hairs, some fat and round and some relatively thin; there were also some mite nymphs with only three pairs of legs (Fig. 2). Some of the mites had bodies covered in fungal spores. There was a considerable amount of mite faecal excreta. There were also some exoskeletons of dead mites.
Using the mountant containing safranin the following fungi were identified:- Cladosporium spores, Aspergillus and Penicillium spores as well as fungal fruiting bodies on the end of mycelial threads. To identify some of these spores a higher magnification had to be used.
Dust clouds from hay
Some degree of fungal contamination is present in all hays, those that have heated are very dusty and the composition of this dust is mostly thermophilic fungi and actinomyces. The water content of the hay when it is baled can be related to the fungal and mould formation (Clarke, A.F. 1987). If it is baled with only 15 to 20% water it heats up very little. It will be virtually dust free, with some plant debris and pollen grains. A small number of spores will be seen but they will be the normal constituents of the 'field fungi'. Baling hay with 20 to 30% water may lead to temperaturs of 35° to 45°C occurring in the bale with the development of a moderate amount of moulds, which may include a large number of , allergens' and potentially infectious pathogens. If it is baled with an even higher water content, 35 to 5O%, this leads to spontaneous heating as high as 60°C. It is under these conditions that the worst contamination occurs in both hay and straw.
Dust mites add a further complication as they are dependent on fungal spores for their food. Once the spores have been eaten they pass through the intestinal tract of the mites and are excreted as clumps of semi-digested spores in the form of a faecal pellet (see Fig. 1 ). Mites may be found alive in hay stored for over a year, though on occasion they may disappear much earlier.
If the mites disappear the only evidence seen will be faecal pellets and the occasional exoskeleton.
Poor hay quality always has numerous mites and faecal pellets even if the number of spores seen are low.
The range of organisms that are able to be pathogens are: viral, bacterial, fungal and actinomycotic spore clouds, foreign bodies such as plant material, various mites and their excretory metabolites and noxious gases such as ammonia. these contaminants can be pathogenic in a number of ways. They may cause direct infection, be allergenic, behave as primary irritants or simply interfere with the respiratory defence mechanism.
We should be able to prevent the transmission of viral and bacterial disease by ensuing that infected tortoises are separated from all healthy reptiles and are then treated, in the case of bacterial disease, with a suitable antimicrobial drug such as an antibiotic. Respiratory diseases may be transmitted by several different routes other than aerosol dispersal. These include direct contact, nose to nose, and indirect contact via your hands, clothing etc. even on living arachnids. When we consider how fungal and mould spores are spread we must think of not only the degree of contamination of the hay or straw but also be aware of the fact that microscopic mites walk and move about and may easily enter the nasal passages carrying spores attached to their bodies. In the confined space in which we keep our tortoises there is no chance of diluting the numbers of mould spores and mites by maintaining a ventilation as would be done in a loose box or stable for example. the other factor we must not forget is that the interior of the tortoise lung has large alveoli so that the interior looks like a large sponge. Once a mould gets in, there is ample space for it to grow. Once mites enter, their life expectancy is very short and the exoskeleton (the dead ) will remain to act as persistent foreign body. The viability of fungal spores is not essential to their allergenicity. The mites themselves are allergenic as are spores of any age and the semi-digested spores in the faecal pellets.
NO work has been carried out, to my knowledge, on whether tortoises suffer from allergenic reactions.
It is not natural for a tortoise to bury itself in either hay or straw , which are man made. They bury themselves under piles of rotting vegetation, under low lying shrubs, under fallen free trunks, under rocks and stones, in hollows and holes in the ground, under leaf mould and by digging themselves down into the soil. They may well encounter soil bacteria, fungal hyphae and so on in these conditions but they most certainly will not encounter the dust mites, the forage mites and the profusion of fungal spores that exist in poor quality hay and straw.
The smell and macroscopic examination of a hay or straw sample bears no relationship to the microscopic findings. In view of this work it is recommended that neither hay nor straw should be used in tortoise houses, huts or hibernation quarters. Instead use shredded newspaper for the former and either blocks of polystyrene, polystyrene chips or shredded newspaper inside the hibernation box The advantages of polystyrene over newspaper is that it is recognised as an insulating material. At the end of one year's use throw away and dispose of all insulating material and replace it with fresh, new material for the following year' s hibernation.
The author wishes to thank A.F. Clarke for providing the mountant containing safranin and L.A Ford for the artwork.
Clarke, A.F., 1987: In Practice 9, 196-2O4.
Clarke, A.F. & Madelin, T.M., 1987. Equine Veterinary Journal 19, 442-447.
Testudo Volume Two Number Six 1988