Friday, October 30, 2015

Gangrenous dermatitis: a ‘gut disease’?

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Gangrenous dermatitis (GD) is a bacterial disease of chickens and turkeys which primarily affects the skin and tissues below the skin in the abdomen of the bird. Gangrenous dermatitis is bilieved to be caused by species of clostridia, usually Clostridium perfringens or Cl. Septicum,  but many other bacteria have been isolated from Gangrenous dermatitis lesions.

Dr Donald Ritter, director of health services, Mountaire Farms, Inc, speaking at Delmarva Poultry Industry National Meeting, said that the number of flock affected by Gangrenous dermatitis in commercial poultry has been on the rise in the USA in recent years.
Gangrenous dermatitis occurs in poultry flocks raised on built-up litter. Dr Ritter said that historically, this condition has been linked to flocks whose immune systems were impaired by prior infection with infectious bursal disease virus or with chicken anaemia virus, but that many flocks with Gangrenous dermatitis today appear to have protection against these viruses.

Broiler flocks with Gangrenous dermatitis experience a sudden increase in mortality at 5-7 week of age – up to 1% daily for up to 2 weeks. Turkey flocks experience a similar mortality pattern but from 12-20 weeks of age. It is rare to find birds with Gangrenous dermatitis lesions alive.

Clostridia are spore-forming and so they can persist in the environment for long periods of time and are resistant to most disinfection procedures. Once affected by Gangrenous dermatitis, many houses envolve into endemic Gangrenous dermatitis sites where the disease recurs in most flocks. There is also a seasonal pattern observed in the incidence of Gangrenous dermatitis cases in chicken: the greatest number of cases occurs during spring and summer. Penicilin is the treatment of choice.

Gangrenous dermatitis skin lesions consist of dark purple areas with excessive red thickened serous exudate (‘jelly’) with associated emphysema (‘gas’) in subcutaneous tissue around the hips, abdomen and occasionally the wings in chickens. Typical skin lesions are located in the tail head area of turkeys. Some lesions are close to skin scratches in de-feathered hip areas.

Because Gangrenous dermatitis lesions are often found close to damaged areas of skin caused by toe-nail scratches, the presumed route of infection has been through the damage skin. The localised skin infection then produces bacterial toxins that quickly kill the bird. However, many birds with Gangrenous dermatitis lesions have intact skin in affected areas, or may have lesions on the wings or crop areas of the bird also unaffected by skin damage.

Clostridia form part of the normal anaerobic intestinal flora of poultry, so the itestine provides another possible direct route of infection. The bacteria may enter the bloodstream via mucosal disruption in the gut. Damage to the gut caused by coccidia has been proposed as a source of Gangrenous dermatitis infection.

 Dr Ritter conclude, “I believe that Gangrenous dermatitis will be proven to be primary ‘gut disease’ when all field and research data have been collected and carefully scrutinised. (Watt publishing)
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Another good reason to control houseflies: they carry bird ‘flu virus’

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Houseflies

Avian influenza has taken a great toll on the human population and on the poultry industry over much of the world. One aspect that has occupied scientist is the possible method of transmission, of which there appear to be many. Wild birds have received much oh the attention until now but studies shows that flies can be virus carriers too (Dr Terry Mabbett)

Poultry farms and houseflies need no introduction. Universal infestation by Musca spp. and close relatives is part and parcel of livestock production, especially in hot climates. Musca domestica (common houseply) is a dipterous insect of cosmopolitan distribution and versatile within its environment, feeding and breeding on all kinds of organic matter including food and animal feed, garbage, faeces, sewage and animal carcasses.
Houseflies constantly move between ‘dirty’ areas of putrefaction teeming with pathogens and ‘clean’ areas including feed storage and animal housing. As such they are a major source of disease and implicated in the transmission of over 30 different diseases caused by bacterial, protozoan and virus parasites.

Adult flies carry disease

Houseflies breeding in media brimming with bacteria, including pathogens, might be expected to convey at least some from the larval (maggot) stage to the adult fly emerging from the pupa case. But early research showed the hostile chemical nature of the larva gut and antagonism by gut microflora maintained a generally low level of pathogens. More than one-fifth of houseflies and almost tow-fifth of green bottle blowflies (Lucilia spp) were sterile on emergence.

The main risk of disease spread is from adult houseflies contaminated with bacteria, protozoa and virus particles. Houseflies could theoritically transmit pathogens on their feet but opportunities for attachment to such small surface areas are considered tiny and microbes are susceptible to dessccation.
Hazards are focused on housefly feeding, sucking up liquid from putrefying food and faeces supporting high concentrations of pathogens. Transmission via vomit drops presents risks, but adult houseflies vomit originates from sugary fluids stored in the crop and presents a correspondingly lower risk than excretory deposits. Research which showed Salmonella typhimurium multiplying in the mid-and hind-gut and passing out intermittenly over an interval of at least one week lent huge weight to these arguments.
Houseflies are well established vectors of food poisoning bacteria like Salmonella spp. and Eschericia coli harboured by birds. More recently, transmission of poultry virus diseases like Newcastle disease and avian influenza (AI) by houseflies is considered, in addition to spread by direct contact by contaminated faeces and bird secretions.

Houseflies carry virus disease particles

Recent research at North Carolina State University has shed new light on the role of Musca domestica in the potential transmission of Newcastle disease virus (NDV). Adult flies carried an infectious dose in the gut for three hours after feeding and researchers Drs Wes Dawson and James Guy considered this might be important for spread of the virus when fly populations are high and in contact with highly virulent velogenic NDV strains.

Newcastle disease virus is dedicated disease of poultry but AI is now under the spotlight because the H5N1 highly pathogenic strain is a zoonosis transmitted to human from animal. The march of H5N1 has been far and fast leaving precious little time to study infection and spread in detail. H5N1 virus spread by wild birds is a relatively recent focus since the Qinghai strain H5N1 appeared in wild fowl in western China during may 2005 and subsequently sped all the way to Western Europe and West Africa in just six month.
There are several reported instances going back 20 years of houseflies carrying the AI virus and suspected as a mode of transmission. In 2005, they were highlighted and summarised by scientists from Novartis Animal Health as part of an article reinforcing the importance of good fly control on poultry farm.
Following reports in 1985 of houseflies in poultry houses contaminated with AI, a detailed study was presented at a conference in Australia in the following year. The study was based on a serious 1983/4 outbreak of H5N2 in Lacaster Country, Pennsylvania, USA. Up to 90% of affected flocks died and various modes of transmission, including direct contact between birds, mechanical vectors and vector insects and especially houseflies, were considered.

Fifteen different insect species-mainly flies and beetles- were collected in 300+ species-specific samples, each containing 10-60 insects. More than one-third of the adult Musca Domestica samples contained AI virus particles, as did one-third of samples comprising less abundant fly species like Ophyra (dump flies) and Coproica (dung flies).
During the 2004 H5N1 outbreak, Asian scientists identified the virus in blowflies caught near a poultry farm in Kyoto in western Japan, which had experienced a disease outbreak in the preceding months.

Parallels with West Nile virus

If the AI virus is present in Musca Domestica or other flies, it does not necessarily mean transmission to poultry, let alone extra risk of human infection. However, the possibility of spread by flies does open a whole new dimension on this virus disease. A comparison can be drawn with West Nile virus (WNV), a flavivirus causing disease in wild birds, horses and humans and transmitted amongst theese three groups by the blood-sucking activity of mosquitoes, mainly Culex spp

West Nile virus is a zoonosis and an arbovirus, a virus particle transmitted by an arthropod animal such as an insect, mite or tick. This efficient means of West Nile virus transmission between humans, wild birds and horses by airborne blood-sucking insects has facilitated a breathtaking speed of spread. From a single case in the West Nile region of Uganda in 1973, the virus now threatens many parts of the world and spread right across North America from New York to California in just three years (1999 – 2002).
That the AI virus can be spread by winged insects as well as wild birds underlines the need for efficient fly control on poultry farm, along with other stric biosecurity measures.
Dr. Terry Mabbet, Potters Bar
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Thursday, October 29, 2015

Testing a probiotic mixture for broiler chickens

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Report of a trial in Bulgaria testing the effects of a mixture of probiotics, yeast and organic on the growth and gut health of broilers. The experimental mixture resulted in a shift in the microbial balance in the gastrointestinal tract in favour of Gram-positive bacteria. There were also significant emprovements in both final weight and feed conversion

It is known that the disorder in the compostion of normal gastrointestinal microflora in animals can lead to excessive proliferation of E. coli and coliform baceria, followed by various pathoglogies. A diet of skim milk powder, soybean meal or fishmeal has high acid binding or buffer capacity. This attribute, together with high intestinal pH, allows pathogenic Gram-negative bacteria such as E.coli and coliform bacteria to colonise the digestive tract causing inflammation and digestive disorders, so the gut absorbs fewer nutrients.

Balancing the gut microflora

In stressed birds, the number of E.coli in the gastrointestinal tract increases together with intestinal pH, thus decreasing Gram-positive microflora and producing dysbacteriosis of Gram-negative pathogenic bacteria that colonise intestines, cause inflammation of intestinal mucosa, decreasing the absorption of nutrients and stunting the growth of birds.
In some instance, the continuous administration of high doses of antibiotics or the use of sub-therapeutics or the use of sub-therapeutic doses of antibiotics was followed by dysbacteriosis and infection with Proteus, Pseudomonas and Aspergillus spp. As well as Candida albicans and other pathogens. A level of E.coli  of more than 300.000/m3 air causes microbial stress and may lead to an outbreak of colibacillosis in chickens.
In recent years, numerous studies have been carried out, with the aims of normalising the intestinal microflora composition and preventing the animal’s gastrointestinal tract from being colonised by pathogenic organisms. The activities of Lactobacillus bugaricus and Streptococcus thermophilus  were found to inhibit enteropathogenic E.coli in vitro. It is sometimes recommended to supplement poultry feeds with lactic acid, bacteria and yeast at times of stress. Some data has demonstrated that an acid environment (pH 3.5-4.0) favours the development of lactobacilli and inbibits the replication of E.coli, salmonella and other Gram-negavite bacteria known to cause gastrointestinal diseases. Acidic additives are especially useful for young animals because they reduce the Gram-negative bacteria and increase the Gram-positive organisms, leading to improvements in the health and weight gain of the animal. A combination of organic acids and probiotics has had synergistic influences on these two parameters in broiler chickens.

Previous work in Bulgaria

We have found out that lactic acid bacteria (L. bulgaricus) and Str. Thermophilus inhibited E.coli, S. enteritidis, St. aureus and Listeria monocytogenes. The inhibitory effect was measured by the diameter of the sterile zone around the well containing the probiotic. The suspension experiment revealed that this probiotic inhibited the count of the aforementioned pathogens by up to 99% in combined vultivation. All this is important for the colonisation of the gut with pathogenic micro-organisms and their adherence to intestinal mucosa epithelium.
The results of our studies showed 4% citric acid and 4% tartaric acid inhibited the growth of several Gram-negative bacteria such as E.coli, Proteus spp, Pseudomonas spp, S, entiridis and some Gram-positive organisms like L. monocytogenes and St. aureus. These organic acids reduce considerably the contamination of litter with such organisms and simultaneously, neutralise ammonia production. At the same time, the balance between Gram-positive and Gram-negative micro-organisms is optimised and the risks of re-infection and microflora imbalance are diminished.
The data from our experiments showed a huge inhibiroty effect over the 90% on the E. coli count in the feed. The highest effect recorded was more than 99% in the probe with the probiotic mixture, which was though to be due to a synergism between the active componenst. There was a correlation between this effect and a lo pH.

The latest study

The trial, with a total of 60 birds, showed that Gram-positive bacteria accounted for only 10% of the microbial microflora, while Gram-negative organisms made up 90% of the microflora in the control group of broilers. In the experimental group, treated with probiotic (3% lactic bacteria plus 1% bakers yeast) plus organic acid (0.7% citric acid) in the feed troughout the growing period, Gram-positive bacteria predominated (77-80%). The control birds had between 3 and 5 times more E. coli per gram of colon that the experimental birds at 20 and 42 days of age. They also had a coliform count at 20 days that was more than six times that of the treated birds and a yeast count of between 12 and 250 times higher than the birds receiving the combined probiotic mixture.

In conlclusion

The maintenance of an optimal balance between Gram-positive (77-80%) and Gram-Negative (20-33%) microflora in the avian gastrointestinal tract as well as good health and performance can be achieved in broilers with a combination of probiotics, yeast and organic acids in the feed.
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