Co-infection of cattle with Fasciola hepatica or F. gigantica and Mycobacterium bovis: A systematic review

Abstract

The liver flukes, Fasciola hepatica and F. gigantica, are common trematode parasites of livestock. F. hepatica is known to modulate the immune response, including altering the response to co-infecting pathogens. Bovine tuberculosis (bTB), caused by Mycobacterium bovis, is a chronic disease which is difficult to control and is of both animal welfare and public health concern. Previous research has suggested that infection with liver fluke may affect the accuracy of the bTB skin test, but direction of the effect differs between studies. In a systematic review of the literature, all experimental and observational studies concerning co-infection with these two pathogens were sought. Data were extracted on the association between fluke infection and four measures of bTB diagnosis or pathology, namely, the bTB skin test, interferon γ test, lesion detection and culture/bacterial recovery. Of a large body of literature dating from 1950 to 2019, only thirteen studies met the inclusion criteria. These included studies of experimentally infected calves, case control studies on adult cows, cross sectional abattoir studies and a herd level study. All the studies had a medium or high risk of bias. The balance of evidence from the 13 studies included in the review suggests that liver fluke exposure was associated with either no effect or a decreased response to all of the four aspects of bTB diagnosis assessed: skin test, IFN γ, lesion detection and mycobacteria cultured or recovered. Most studies showed a small and/or non-significant effect so the clinical and practical importance of the observed effect is likely to be modest, although it could be more significant in particular groups of animals, such as dairy cattle.

Fascioliasis may promote tuberculous infectivity in small ruminants

“…Moreover, hypersensitive skin tests like the cervical intradermal tuberculin test and comparative intradermal tuberculin are seldom practiced in the small ruminants industry due to the thinness of the skin. Furthermore, lesion detection and bacterial culture also confer poor applicability of TB detection technology in live animals ( Howell et al, 2019 ). The development of technologies for the detection of TB in live small ruminants is a big deal, and detection of lesions or tuberculous organisms at necropsy are acceptable alternatives.…”

Prevalence of bovine tuberculosis in slaughtered cattle and factors associated with risk of disease transmission among cattle handlers at Oko-Oba Abattoir, Lagos, Nigeria

“…The difference may be due to the fact that the detection of bTB lesions, in particular, depends on the diligence and thoroughness of the inspector conducting the examination [ 27 ]. Other factors that may influence the detection of tuberculous lesions in abattoirs might include underlying parasitic infections [ 28 ] and other irregularities of abattoir meat inspection [ 29 ]. Hence, cases of missed bTB lesions are a possibility.…”

Review on Bovine Tuberculosis: An Emerging Disease Associated with Multidrug-Resistant Mycobacterium Species

“…In addition, co-infection with bovine viral diarrhea (BVD) virus has conflicting effects in previous studies; it is suggested to suppress the immunological response to PPD or cause rapid progression of bTB or even to have no significant effect [ 46 ]. Furthermore, co-infection with liver fluke, Fasciola hepatica and Fasciola gigantica , may affect the accuracy of bTB but the direction of the effect differs among studies [ 49 ]. It is suggested that liver fluke infection may suppress the M. bovis infection [ 46 ].…”

“…It is suggested that liver fluke infection may suppress the M. bovis infection [ 46 ]. Howell et al examined the evidence to determine the effect of liver fluke infection on four outcomes relevant to bTB diagnosis: TST, IGRA, lesion detection, and bacterial culture [ 49 ]. The study supported the hypothesis that liver-fluke-infected animals are likely to have a reduced response to both TST and IGRA tests and fewer bacteria recovered/cultured from their lesions.…”