# Progress on Necrotic enteritis vaccine



## seminole wind (Aug 22, 2015)

Progress made towards a necrotic enteritis vaccine

Apr 7, 2016 1727 1 

US researchers have evaluated the use of a novel live vaccine to prevent necrotic enteritis in broilers.

Progress made towards a necrotic enteritis vaccine

Necrotic enteritis (NE), is a serious and often fatal disease for chickens and turkeys, with up to 50% mortality reported before effective control measures were introduced. A less severe, but economically important, form of this disease has also been identified and is frequently called subclinical NE.

Impact of NE on poultry

NE is caused by the bacterium Clostridium perfringens, which proliferates in the small intestine and produces potent exotoxins that damage the gut lining, leading to necrosis (death of tissue), ulceration and inflammation. In affected birds, the C. perfringens may also invade the liver to cause acute or chronic hepatitis which results in either death, or subclinical disease, and condemnation of carcasses in the slaughter plant. Thus, NE is a disease which has a significant adverse impact on bird health and well-being, as well as on profitability for the producer.

The disease can be controlled by incorporation of antibiotic growth promoters (AGPs) in the feed. AGPs are effective in preventing NE, but they have been banned in many countries and their use is rapidly being phased out in the US.

Vaccination against NE a good strategy

NE is expected to become a much bigger problem in the US, as has been the experience in other countries following the cessation of use of AGPs. Alternative preventative measures are needed, and vaccination is a good alternative strategy.

The objective of the USPOULTRY-funded study was to test a non-virulent NetB and alpha toxin producing strain of C. perfringens as an orally administered vaccine. NetB and alpha toxin are two of the toxins produced by C. perfringens that are thought to be involved in producing NE. The approach was to administer this unique NetB positive non NE producing strain of C. perfringens by the oral route, with or without mucosal adjuvants, and to test for protective effects by measuring antibody response and exposure to a challenge model for clinical NE.

Three vaccines tested on poultry

Two experiments were carried out. In the first experiment, birds were vaccinated for five days with one of three test vaccines, and subsequently exposed to a disease challenge system. A statistically significant antibody response was measurable in vaccinated birds, which was encouraging. The use of cholera toxin (CT) as an adjuvant produced the best result.

However, the test vaccines did not completely protect the birds against the severe disease challenge system employed. An additional group had been 'vaccinated' with a virulent strain, and approximately 50% of these birds did not develop lesions when subsequently challenged.

In the second experiment, birds were vaccinated at selected discrete time points. CT was again used as an adjuvant but at a higher dose. New adjuvants were also used, and the new vaccine regimes invoked a better antibody response. Some of the vaccinated groups were partially protected from the disease challenge; however the number of birds developing lesions in these groups was too high to make those vaccine formulations applicable in the field.

Live vaccine potential

Nonetheless, the results confirmed the potential for this strain as a live vaccine since it did not produce any adverse effects on the birds and it was able to reduce the incidence and severity of lesions after disease challenge. Future efforts should focus on the use of improved adjuvants for optimising the protective effects of this live vaccine


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## MikeA_15 (Feb 21, 2016)

I remember reading about this from the Poultry Science Association. It will be interesting to see what develops. I can't stress the importance of probiotics and vitamin-mineral supplements in a chicken's diet, and the fact that Clostridium Perfringens is opportunistic, and isn't generally the catalyst for necrotic enteritis since it most often occurs after Coccidia have caused damage to the intestinal tract. Preventing Coccidiosis/intestinal worms does much in the prevention of necrotic enteritis.


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## seminole wind (Aug 22, 2015)

Hey Mike! You really know your stuff! There was actually 1 time when I lost 3 to NE in 2 days. I think their immune system was not that great from their genes. A week later everyone got a one-eye infection and a few more died from that. It was really sad. I had 2 hatches of Crele Polish from different people. Hatched a total of 13, and now have 2.

That's the thing with NE. They can have no symptoms and just drop dead. The three I had actually hemorrhaged without any symptoms prior to it.


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## MikeA_15 (Feb 21, 2016)

I'll look for some more info I have about Clostridium and post it when I have a few minutes.


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## MikeA_15 (Feb 21, 2016)

Here you go. It confirms what I mentioned but in much better detail:
http://www.worldpoultry.net/Breeder...enteritis-away-from-poultry-flocks-WP007497W/

*Keeping Clostridial enteritis away from poultry flocks*

May 26, 2010 update:Jun 14, 2010 
Clostridial enteritis affects intestinal health in broiler flocks and may cause considerable losses. It is caused by Clostridium perfringens and is found all over the world. Fighting the disease is a continuing challenge for the poultry sector. Preventive actions using dedicated products are a valuable solution to maintain healthy gut flora.

*By Dr. Tom Verleyen, Kemin Agrifoods Europe, Herentals, Belgium*
Growth retardation around the third week of age associated with impaired intestinal health is a major problem in broiler production, fully recognised by farmers, veterinarians and nutritionists. This problem occurs so frequently that it is no longer considered as a disease by some veterinarians. Issues of _Clostridial enteritis _are prevalent in the broiler industry worldwide. The pathogen involved is _Clostridium perfringens_.
*Manifestation of necrotic enteritis*
_Clostridium perfringens_ infections in poultry may show up as an acute clinical infection or by a subclinical infection. The acute form of the disease leads to increased mortality of the broiler flock, which can account for high losses of up to 1% per day, reaching mortality rates up to 50%. Clinical signs include depression, ruffled feathers, diarrhea and evident macroscopically lesions in the small intestines. The clinical form of necrotic enteritis is easily detected and luckily occurs quite seldom in flocks and can be treated. In the subclinical form of the disease, damage to the intestinal mucosa caused by _Clostridium perfringens _leads to decreased digestion and absorption of nutrients, reduced weight gain and increased feed conversion. The subclinical form of necrotic enteritis is the most important as it occurs predominantly and has most significant economic impact due to impaired growth rate and feed conversion.
Typical signs seen by poultry producers are specific growth retardation around the 23rd day of age (_Figure 1_). Litter quality changes and becomes more wet, leading to moisture levels above 40% and often undigested feed particles are found in the litter. Consequences of poor litter quality are obvious, as it leads to increased issues of foot pad lesions, hock lesions and breast blisters resulting in higher levels condemnations at the processing plant.
*Causative bacteria, occurrence*
_Clostridium perfringens_ is a commensal organism in the intestinal tract of poultry, colonising in the early phase of life of the animals. It is a gram positive anaerobic spore forming bacterium, able to produce various toxins and enzymes responsible for the associated lesions. Clostridium can be classified in five types (A, B, C, D and E), with type A being the most predominant cause of Clostridium infections in poultry. For a long time it was accepted that the alfa toxin is responsible factor, but new research indicates that Net B is related to the causative form of necrotic enteritis.
Chickens generally take up _Clostridium perfringens_ from the environment, such as feed, water, soil etc. Inoculation of animals with _Clostridium perfringens_ does not lead per se to the development of necrotic enteritis. One or several predisposing factors may be required to elicit the clinical signs and lesions of necrotic enteritis.
Studies showed that the subclinical form of necrotic enteritis is a worldwide problem with an average of 80% of the flocks having had Clostridium diagnosed (_Figure 2_). A follow-up study in 2005 indicated an increased incidence of _Clostridial enteritis_ in all regions of the world. Recent European surveys have confirmed the severity and the widespread of the problem.
*Impact on animal performance*
_Clostridium perfringens _associated necrotic enteritis may appear with variable degrees of severity (_Table 1_). Birds acutely infected with Clostridium perfrigens will show high mortality rates up to 30% of the flock. The clinical form of _Clostridium perfringens_ is easily seen and can quickly be treated through medication. However, as the disease occurs at subclinical level, where mortality is not substantially increased but with clear signs of intestinal disorders, then it becomes more difficult to quantify the impact. At subclinical level, _Clostridium perfringens _are known as a serious profit killer, leading the FCR to increase with 6-9 points and final body weight to reduce between 3-5%. As subclinical necrotic enteritis is not always detected in the broiler flock there is a serious risk that it can pass unnoticed and affect broiler production. Annual losses to producers in the US and Canada due to subclinical necrotic enteritis are estimated to be $1.5 up to 5 cent per bird, according to a study reported in World Poultry in 2000.
*Predisposing factors*
There are several predisposing factors that producers need to be aware of and continuously monitor and try improve on. These are namely infectious causes, nutritional factors, and preventative measure.

*Infectious causes*
The most important known predisposing factor is intestinal damage caused by coccidial pathogens. Intestinal damage by Eimeria results in initial damage of the gastro intestinal lining, which is further used by _Clostridium perfringens _for additional proliferation. Coccidiosis is often seen to occur just prior to or during a necrotic enteritis outbreak. Inflammation of the gastro intestinal tract or a disruption of the gastro intestinal balance due to an infection often leads to the development of _Clostridium perfringens_.
*Nutritional factors*
Dietary factors are very important in order to control the actions of Clostridium. Diets with high levels of indigestible, water-soluble non-starch polysaccharides (e.g. coming from rye and wheat) are known to increase the viscosity of the intestinal content, which encourages the development of necrotic enteritis. Also diets rich in high levels of proteins such as fish meal give an excellent amino acid source to Clostridium, which is known as a predisposing factor.
As Clostridium lacks the ability to produce 13 out of the 20 essential amino acids, its growth is therefore enhanced in an environment rich with proteins. Besides these factors, several other nutritional factors have an influence on necrotic enteritis. Basically, all diets with an imbalanced nutritional content can predispose necrotic enteritis. Diets with a low energy to protein ratio lead to a higher feed consumption and will result in an excessive protein intake and thereby increase the nitrogen level in the digesta and excreta. Similarly, poorly digested proteins in the lower gastro intestinal tract act as a substrate for the microflora. In order for efficient excretion to take place the animals need to take in larger quantities of water, but then the litter tends to become wetter with a higher level of nitrogen. This allows the opportunity for pathogenic bacteria such as_ Clostridium perfringens _to proliferate in the litter, which is likely to exacerbate the problems. Any factor that stresses the broiler chickens gastro intestinal tract is a risk for _Clostridium perfringens _proliferation. There is evidence to suggest that alterations in feeding regimes cause stress in the gastro intestinal.
*Preventive management*
There are clear indications that _Clostridial enteritis_ is under-diagnosed and treated too late. When a watery intestinal content and wet litter are observed, Clostridium already has already proliferated. The traditional method of managing _Clostridial enteritis_ has been through the use of antibiotic growth promoters (AGPs). Preventive actions through products with selected activity against _Clostridium perfringens _before the first symptoms are observed to be a valuable solution to maintain a healthy gut flora.


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## seminole wind (Aug 22, 2015)

I've read that one. I get the World Poultry email magazines too. It can be some good info at times to read about what the pros are doing.


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## Sylvester017 (Nov 2, 2013)

*NE*



seminolewind said:


> I've read that one. I get the World Poultry email magazines too. It can be some good info at times to read about what the pros are doing.


Hi seminolewind and Mike A

Is NE something to be really concerned about in small backyard flocks or is the malady only prone to closely confined poultry industry meaties or large breeding hobby flocks? It seems like every time I do a little bit of research (just enough to be dangerous lol) I find yet another malady that can affect our U.S. chickens. As if AI, fowl pow, cocci, worms, CRD issues, Marek's and/or cancer, reproductive issues, etc, weren't enough?


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## seminole wind (Aug 22, 2015)

NE is caused by bacteria known as Clostridium Perfingens (sp). However low immune system, worms, E.coli, Coccidiosis can go hand in hand with it.. Problem with it is that it can go un noticed. Just unthrifty chickens, poor egg layers. They call that chronic low level infection. Then, some can just drop dead. I had 3 that just dropped dead and when I picked them up, blood came pouring out. 

My chickens have some immunosuppression due to Marek's virus exposure. So any time they look not right, I give them meds that will cover Clostridium as well. 

It can be in laying houses as well as backyard chickens. It's been known to be more common now than years ago. So yes, it can be a problem for small flocks as well. Your best bet is to read the articles above and know something about it . 

Oh and you can add Marek's virus onto your list. : (


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## MikeA_15 (Feb 21, 2016)

Hi Sylvester,
Many diseases can be avoided by good management practices. One of them being a closed flock. That means no new birds introduced to your existing flock, and if you must, make sure new birds are quarantined to a separate area for a minimum of 1 month to make sure they are pest and disease free. It is also best to not mix young birds with old birds. If you allow a hen to hatch her own eggs, let that be in a separate pen away from the adult flock. Only breed from birds that are yearlings and are proven to demonstrate strong immunity and uniform egg production. Knowing when and what to supplement birds' diets with makes a difference when it comes to growing, building immunity which all begins in the gut. There are a number of good practices I've adopted for the betterment of raising birds over the years, so if you have questions, I'd be happy to offer some information.


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## seminole wind (Aug 22, 2015)

Michael, said really well. That's the way to bypass a lot of diseases. Except Cocci and NE. The bacteria are just all over the place normally and just waiting for a run down chicken. Worming and dusting, cleanliness, and proper feeding keeps them healthy.

I would keep a closed flock. My closure is eggs hatched at home, or day old chicks from a hatchery.


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