The diversity and range of helminth parasite groups represented in the peramelids resembles that of dasyurids in many ways. The major groups of nematodes in these marsupials consist of the superfamilies Trichostrongyloidea, Metastrongyloidea and superfamilies of the order Spirurida (Beveridge and Spratt, 1996). Additionally, a range of trematode parasites have been recorded whilst cestodes consist of the families Hymenolepididae, Dilepididae and Linstowiidae (Beveridge and Jones, 2002), all of which generally have insects as intermediate hosts (Beveridge and Spratt, 1996). However, no trematode or cestode parasites were detected in I. obesulus or P. bougainville for this study, which was most likely due to the use of a flotation technique for the examination of faecal samples.
Strongyle nematodes were detected in the faeces of I. obesulus and P. bougainville at similar prevalences (68.8% and 60.0% respectively) despite the P. bougainville being sourced from a captive breeding colony. Trichostrongyloid nematodes constitute the most diverse helminth superfamily in the bandicoots comprising three families; Mackerrastrongylidae; Dromaeostrongylidae and Herpetostrongylidae (Beveridge and Spratt, 1996). The peramelids are typically dominated by the family Mackerrastrongylidae which is represented by the three genera: Asymmetracantha;
Mackerrastrongylus; and Tetrabothriostrongylus (Beveridge and Spratt, 1996; Spratt et al., 1990). Each of these genera has been recorded from I. obesulus but not from P. bougainville, however they have been recorded in other species of Perameles (Spratt et al., 1990). Additionally, the representative genera of the Dromaeostrongylidae and Herpetostrongylidae families have also been recorded from I. obesulus (Spratt et al., 1990).
Three I. obesulus from Manjimup were found to have Strongyloides-like eggs or L1 larvae though none were detected in any of the P. bougainville. A single species,
Parastrongyloides australis, has been recorded as occurring in I. obesulus (Mawson, 1960). Parasites of the family Strongyloididae typically have direct life cycles and involve a free-living stage where infection of the host occurs via ingestion or skin penetration of L3 larvae. The sourcing of P. bougainville from a captive breeding colony may explain the absence of these parasites, as the management of this P. bougainville population included periodic anthelminthic treatment which could have broken the life cycle and contributed to the elimination of these parasites from these animals. However, the prevalence of these parasites in the wild I. obesulus populations sampled was still low (3.9%).
The occurrence of spiruroid nematodes in only three of the 77 wild I. obesulus (3.9%) appears to be significantly lower than its occurrence in nine of the 35 captive P. bougainville (25.7%). These parasites typically have an indirect life cycle involving arthropods as intermediate hosts and spiruroid larvae have previously been reported to occur in I. obesulus, though none have been identified to species level (Spratt et al., 1990). The higher prevalence of spiruroid nematodes in P. bougainville as opposed to I. obesulus in the present study could be related to their captivity. The constant presence of a readily accessible food source would be expected to attract numerous insects and
Similarly, the difference in prevalence of Trichuris between I. obesulus (11.7%) and P. bougainville (22.9%) may also be due to the influence of captivity. Whilst Trichuris
species have direct life cycles, periodic anthelminthic treatment would most likely not be intensive enough to control infections. Therefore, the captive bandicoots would be continuously exposed to infective stages, which would be exacerbated by the movement of both animals and soil/bedding. Although the species of Trichuris in the bandicoots was not determined, T. peramelis is the only species of this cosmopolitan genus described from marsupials (Beveridge and Spratt, 1996), and has been reported in several species of the bandicoot genera Isoodon and Perameles.
The parasite genus Linstowinema is represented by four species and is endemic in Australian marsupials (Beveridge and Spratt, 1996). This nematode genus is commonly found in peramelids (Beveridge and Spratt, 1996), and was present in 37.7% of I. obesulus and 11.4% of P. bougainville sampled. Only one species of Linstowinema (L. cinctum) has previously been recorded for P. bougainville, though in the present study all four infected P. bougainville were identified as harbouring L. inglisi. Five of the 29 infected I. obesulus were harbouring L. inglisi, whilst the remaining infections were an unidentified species of Linstowinema. Two species (L. inglisi and L. meridionalis) as well as a third unidentified species of Linstowinema have previously been identified in
I. obesulus (Spratt et al., 1990).
The detection of oxyuroid nematodes in a single P. bougainville is unusual as these nematodes typically occur in herbivorous and/or folivorous diprotodonts (Beveridge and Spratt, 1996), whilst several species of lizard are also parasitised by oxyuroid nematodes (Pichelin et al., 1999). The occurrence of this parasite in only a single P.
bougainville suggests that this is an accidental infection, most likely resulting from the ingestion of soil contaminated with oxyuroid eggs or an infected lizard attracted to the readily available food in the breeding pens.
Both I. obesulus and P. bougainville had the widest range of protozoan parasites of the host species sampled in the present study. Unidentified species of Entamoeba and
Eimeria species were present in both I. obesulus and P. bougainville at similar prevalences. Whilst these two parasite genera have previously been recorded in I. obesulus, there are no records for P. bougainville and neither of these protozoan parasites have been recorded for other members of the genus Perameles (O'Donoghue and Adlard, 2000). Giardia was detected in only a single I. obesulus from Manjimup, though Bettiol et al. (1997) found Giardia in 62% of bandicoots examined from Tasmania. Giardia was also detected in a dingo (Canis lupus dingo), a pale field rat (Rattus tunneyi) and a western chestnut mouse (Pseudomys nanus), all collected from Lake Argyle (results not shown). These results, along with that of the Giardia found in the I. obesulus, are further discussed in Chapter 4.