Studies on the interaction between anthelmintics and immunity to Dictyocaulus viviparus
Başlık:
Studies on the interaction between anthelmintics and immunity to Dictyocaulus viviparus
Yazar:
Bonazzi, Eduardo Francisco, author.
ISBN:
9780438053366
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (158 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: J. Armour.
Özet:
In Section 1 of this thesis the literature pertaining to Dictyocaulus viviparus is reviewed with particular reference to its life-cycle and pathogenesis, epidemiology, treatment and control. The problems surrounding control, other than by vaccination are discussed and the need for further studies on the interaction between immunity and anthelmintic treatment highlighted. The techniques used in the experimental procedures are explained in detail in Section 2 while the experimental design, results and findings of the experiments carried out are given in Sections 3 and 4. In Section 3, the results of an experiment are presented in which a 16-day infection of D. viviparus in two groups of calves was treated with levamisole and fenbendazole respectively. Five days later the calves were reinfected with 4000 infective larvae and necrospied 21 days post-infection. Although the lungworm burdens of the two groups of calves were reduced by about 69 per cent compared to a control group, the clinical signs of dyspnoea, tachypnoea and coughing which ensued following reinfection were indistinguishable from those in the controls given a primary infection. These clinical reactions were due to pulmonary emphysema, oedema and an acute epithelialising pneumonia apparently associated with the death and disintegration of lungworms in situ. when these results are compared with those previously obtained by Dictol lungworm vaccination it was concluded that control based on "infection and anthelmintic therapy" does not offer an acceptable alternative to prophylaxis by vaccination. In Section 4, the results of two experiments are reported. In the first, the immunity produced by two doses of 1000 D. viviparus larvae subjected to gamma radiation (40 Kr.) is assessed by challenge with approximately 2000 L3, of the vaccinated calves and a control group at one month post vaccination. The mean lungworm burdens established following challenge of the vaccinated calves was only 93 compared with a mean of 878 in the controls. Although this reduction in the number of lungworms established was highly significant, it is slightly less than the regular achieved following vaccination of calves with X-irradiated larvae of D. viviparus. While this difference may be a reflection of the radiation source used i.e. gamma versus X-rays, it was concluded that the presence of an intercurrent pneumonia due to Mycoplasma infection was more likely to have lowered the immunity resulting from vaccination. In the second experiment of Section 4, 7 groups of helminth-naive calves were used. Four groups of 4 calves each were vaccinated as in the first experiment with two doses of gamma irradiated larvae at an interval of one month and the 3 remaining groups (2 of 4 calves each, 1 of 5 calves) acted as controls. To simulate the two principal epidemiological situations thought to exist in the field, two of the vaccinated and two of the non-vaccinated groups received a low level "trickle" challenge of 800 D. Viviparous L3 over a four-week period prior to a single large challenge with approximately 2000 L3 some four months post-vaccination. The remaining groups received only the single large challenge. In addition, two of the vaccinated groups (one receiving the trickle infection, one not) and one control group were given a rumen bolus programmed to release the anthelmintic morantel tartrate over a 90-day period. This bolus was given two weeks post-vaccination and prior to any trickle infection. Based on a comparison of the clinical signs, gross pathology and lungworm burdens at necropsy of vaccinates and the challenge control group, vaccination conferred a significant degree of protection (P<0.00l) to subsequent challenge 4 months post-vaccination. The introduction of a trickle infection and/or an anthelmintic slow release device between vaccination and challenge had no effect on the degree of protection engendered. Non-vaccinated calves given a trickle infection with or without an anthelmintic bolus were also highly immune to challenge. Finally, in Section 5 the results of the experiments are discussed in relation to the control of parasitic bronchitis in the field. The conclusion is reached that the control of parasitic bronchitis is best achieved by immunisation with an attenuated larval vaccine and that attempts to integrate the control of both parasitic bronchitis and parasitic gastroenteritis by anthelmintics alone are fraught with danger.
Notlar:
School code: 0547
Tüzel Kişi Ek Girişi:
Mevcut:*
Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684457.1) | 684457-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
On Order
Liste seç
Bunu varsayılan liste yap.
Öğeler başarıyla eklendi
Öğeler eklenirken hata oldu. Lütfen tekrar deneyiniz.
:
Select An Item
Data usage warning: You will receive one text message for each title you selected.
Standard text messaging rates apply.