Experimental Infection withToxocara catiin BALB/c Mice, Migratory Behaviour and Pathological Changes

Abstract

Experimental inoculations of 1000 Toxocara cati larval eggs were carried out in 18 BALB/c mice. The T. cati eggs used for inoculation were collected from the faeces of naturally infected cats. Euthanasia was performed on two mice on days 1, 2, 3, 4, 5, 6, 14, 21 and 28 post-inoculation (p.i.). Tissue samples were taken for digestion and histopathology. Larvae were recovered from all infected mice and the average of all larvae recovered was 28.3% (95%; CI: 14.1-42.4). Maximum number was obtained from liver on days 1 and 2 p.i.; from the lung on day 2 p.i. and from the brain on day 28 p.i. In muscle, the recovery was high as from day 3 p.i., with the maximum obtained on day 28 p.i. Superficial foci of congestion and haemorrhage were macroscopically observed in the lungs between days 2 and 5 p.i. and in the brain between days 3 and 6 p.i. Microscopic lesions were observed in the liver between days 2 and 14 p.i., with periportal and subcapsule inflammatory infiltrates. In the lungs, haemorrhages and inflammatory infiltrates can be observed in the alveolar parenchyma, close to bronchioles and large blood vessels. In the brain, congestive areas without inflammatory reactions were seen. In muscle, the presence of inflammatory infiltrates and degenerated muscle can be observed surrounding a parasite larva. These same lesions were observed in myocardium and pericardium. The kidneys were congested with inflammatory infiltrates. The inflammatory cells present in all the tissues studied were lymphocytes, neutrophils and a few eosinophils. Formation of granulomas or signs of larva encapsulation were not observed. The migratory pattern of T. cati larvae in BALB/c mice and its tendency to become concentrated in the muscle reinforce the importance of the mouse as a paratenic host for the parasite's cycle in the environment.

Toxocara canis larvae reinfecting BALB/c mice exhibit accelerated speed of migration to the host CNS

“…In agreement with Kayes (2006), we confirmed that both visceral and ocular toxocarosis can develop during primary infection by massive parasite infectious dose, though similar clinical picture can develop also during reinfections. The time course of T. cati infections is in agreement with data of Cardillo et al (2009), Olson (1976, Prokopič and Figallová (1982), and Ghafoor et al (1984). We showed that the larvae can invade the brain and eye also during early phase of primary infection.…”

Neurotoxocarosis alters myelin protein gene transcription and expression

“…Furthermore, earlier activation of OPCs in T. cati infection might reduce or prevent histologically and clinically apparent signs of demyelination and therefore may explain why these animals developed clinical symptoms and histologically apparent signs of demyelination much later than T. canis-infected individuals. On the other hand, this histological lack of demyelination and clinical symptoms may simply be due to lower numbers of T. cati larvae reaching the brain as they accumulate in muscle tissue mostly (Cardillo et al 2009;Janecek et al 2014), which likely results in minor neuropathological effects compared to T. canis. Additionally, other genes such as Mag are solely affected in T. canis-infected mice in both cerebra and cerebella.…”

“…In cerebella and cerebra of T. cati-infected mice, Cnp is downregulated later, 150 dpi. Since T. cati larvae predominantly accumulate in muscle tissue while only a minor proportion migrates to the brain (Cardillo et al 2009;Janecek et al 2014), it can be expected that clinical symptoms, histological changes and signs of demyelination appear later in the course of infection. Essentially, fewer larvae require more time to accomplish a clinically apparent degree of parenchymal brain damage.…”

“…After oral infection, Toxocara larvae reach the brain as early as 60 h later by perforating vessel walls (Kolbeková et al 2011). Subsequent haemorrhages and tissue migration lead to parenchymal damage (Cardillo et al 2009;Janecek et al 2014). Additionally, blood-brain barrier impairment and upregulation of braininjury-associated biomarkers on messenger RNA (mRNA) and protein level were observed for weeks after T. canis infection (Liao et al 2008a, b).…”

Prevalence of endoparasites in stray and fostered dogs and cats in Northern Germany

“…As Toxocara eggs in the present study have not been distinguished morphologically, we do not know how many of the Toxocara eggs found coproscopically were actually only contaminants from ingested cat faeces. However, it deserves special attention as there is no difference in the zoonotic potential of T. canis and T. cati (Cardillo et al 2009). …”