Immunity Deficiency In Birds And Neonicotinoid Pesticides

This feature is a continuation of an article by Dr Rosemary Mason and Palle Uhd Jepsen. To go to the beginning of the feature, click HERE.

Greenfinches in the UK and Europe

In the UK, greenfinch deaths (maximum number of deaths in the months August to October) from infections with Trichomonas gallinae, a protozoal organism which invades the bird’s crop and mucosal lining of the beak, started around 2005 and has devastated the populations throughout Europe [52].

Apparently, the organism can survive only a matter of minutes outside its host, so if it were spread conventionally it would require direct contact between birds. In August 2009 there were reports of tens of thousands of songbirds, mostly greenfinches, dying in the west of Germany and the deaths spread across the border into the eastern Netherlands [53]. According to Hugh Jansman of Wageningen University, “The canker disease was first described as early as 1500, but was not found in wild songbirds until 2002.” It had been well known as a cause of disease in pigeons and doves, and birds of prey that fed on them, but had never been seen before in songbirds. By 2010, the population of greenfinches in central England had decreased by one third [54] and in March 2011, greenfinches, chaffinches and goldfinches are continuing to die from the disease [55].

Chaffinches in the UK and Europe

In the UK, reports of chaffinches appearing in gardens with white, crusty growths on their legs and feet caused by a papilloma virus began in 2005; the mortality is said to be about 20%, so the disease kills more slowly than with the greenfinch Trichomonas infections [52]. In 2004, two dead chaffinches were found in Europe, one of which was suffering from two diseases. In the Czech journal, pathologists reported one as having a co-infection between papilloma virus (which was also affecting the beak) and K. jamaicenis, a mite [56]. They also commented that “beak papillomatosis is rare in wild birds”.

The Tit Family in the UK

In 2005, acute necrotising pneumonitis with Suttonella ornithocola spp. in the tit family was first reported by researchers in Inverness and the Institute of Zoology (IoZ), London; they found that the gram negative bacterium recovered from the diseased birds represented a novel species [57]. In 2006 there were further reports of mortality from this novel bacterium [58]. In 2010, pathological studies on further cases in tit species were reported in the Veterinary Journal, by Lawson et al. from the IoZ [59]. In a surveillance of garden bird mortality, S. ornithocola was isolated from the lungs of six tits from a total of 82.

Avian pox in Great Tits

The first case was reported in the UK in 2006. Although there had been previously isolated reports in other birds, Great Tits seemed to be affected more severely, with warty tumour-like growths around the eyes and beak, sometimes interfering with feeding.

Tumours on the body can grow quite large. The virus is spread by biting insects and is persistent in the environment. It was first reported in south-eastern counties, Surrey, Sussex and Kent; from there it has spread north and westwards, so that it was first found in Wytham Woods in the Edward Grey Institute near Oxford. Prof. Ben Sheldon, Director of the Institute, said records had been kept there since 1947 and they first detected the disease in 2010. Oxford University are undertaking molecular analysis to see if it is a new strain, or one from Europe. Prior to 2006 it had been reported in Austria, Czech Republic, Slovakia and Scandinavia [60].

Tropical Usutu Virus in Blackbirds

In September 2011, mass deaths of blackbirds were reported in the Rhine-Neckar area of Germany. The Bernhard-Noct Institute for Tropical Diseases and the Friedrich-Loeffler Institute, examined four birds and confirmed that it was the tropical Usutu Virus from Africa. It was first seen in Austria in 2001, then Italy, Hungary and Switzerland. In blackbirds it causes apathy then signs of a central nervous system disorder, with unnatural movements of the head [61].

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