## 3 Results
### Histopathological Lesions in Nasal and Nervous Tissue  
In the nasal epithelium, a significant number of fingerlings infected with _A. lusitana_ (50%) and _A. salmonicida_ (41.1%) showed different histopathological lesions. Congestion with different distribution patterns and high severity grades, focal hemorrhagic epithelium (Figure 1b), moderate multifocal epithelium and hyperplasia of the nasal epithelium and goblet cells, as well as a leukocyte infiltrate of mononuclear and polymorphonuclear cells, were observed (Figure 1c). On the other hand, the histopathological finds of _A. media_ (35.5%), _A. allosacacharophilis_ (30%), _A. caviae_ (28.8%), _A. hydrophila_ (27.7%), _A. besiarum_ (26.6%), _A. sobria_ (20%), _A. veronii_ (11.1%), and _A. popoffii_ (7.7%), present middle-to-less severity and distribution; edema, congestion, goblet cell hyperplasia and, leucocyte infiltration in different grades and, different distributions in the nasal epithelium were observed, with no significant histopathological lesions (_p_ > 0.05). Histopathological lesions in control group were not observed (Table 3). Basophilic aggregates or bacterial aggregations were observed in all fishes experimentally infected with the different _Aeronomus_ species. Basophilic aggregates or bacterial aggregations in the control group was not observed. The main histopathological lesion in the telencephalon consisted of severe multifocal congestion for fish infected with _A. media_ (31.1%), and a moderate degree for the groups infected by _A. salmonicida_ (25.5%), and _A. caviae_ (22.2%). The congestion was observed in focal and multifocal presentation, and also hemorrhagic lesions were present on focal and bifocal distribution, in moderate-to-slight presentation in _A. besiarum_ (21.1%), _A. hydrophilia_ and _A. lusitana_ (18.8%). No significant histopathological changes were observed in _A. veronii_ (10%), _A. sobria_ (7.7%), _A. allosacacharophilis_, and _A. popoffii_ (3.3%), and control groups (Table 3). \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{_Aeronomas_ **Species**} & \multirow{2}{*}{**N**} & \multicolumn{2}{c}{**\% of Fish with Clinical Sign or Behavioral Changes 1**} \\ \cline{3-4}  & & **Darkened** & **Lack of** & **Abmoral Swimming** \\  & & **Skin/Hyperpigmentation** & **Appetite/Inappetence** & **Abmoral Swimming** \\ \hline _A. allosacacharophilis_ & 90 & 0 & 1.11 & 25.55 \\ _A. besiarum_ & 90 & 6.66 & 32.22 & 83.33 \\ _A. caviae_ & 90 & 0 & _38.88_ & 60 \\ _A. hydrophilia_ & 90 & 11.11 & 46.66 & 74.44 \\ _A. lusitana_ & 90 & 0 & 1.11 & 34.44 \\ _A. media_ & 90 & 1.11 & 16.66 & 25.55 \\ _A. popoffii_ & 90 & 0 & 3.33 & 31.11 \\ _A. salmonicida_ & 90 & _18.88_ & 47.7 & 66.66 \\ _A. sobria_ & 90 & 1.11 & 46.66 & 67.77 \\ _A. veronii_ & 90 & 15.55 & 28.88 & 38.88 \\ Control group & 90 & 0 & 0 & 8.88 \\ \hline \end{tabular}  
* Groups in italics within the same column are significantly different (_p_ < 0.05).  
\end{table} 
Table 2: Percentages of clinical signs or behavioral changes, present in fingerlings experimentally infected with different _Aeronomas_ species. On the other hand, the histopathological findings in the oblongata medulla were focal and multifocal congestion, and moderate-to-severe degrees of infection with _A. besiarum_ (40%). No significant histopathological lesions (\(p>0.05\)) were observed for the groups infected with the species _A. Indrophilia_, _A. Insitana_, and _A. media_, _A. veronii_, _A. caviae_, _A. salmonicida_, _A. sobria_, _A. popoffii_, and _A. allosacharophilia_ (Table 3). The fingerling group infected with _A. salmonicida_ presented a mild degree and focal congestion with perivascular mononuclear infiltrate were identified in one fingerling (Figure 1d), but basophilic aggregates were not observed. The percentages of bacterial isolation were obtained from the region in cerebellum and medulla oblongata. Fingerlings were infected with _A. besiarum_ (0.90%), _A. veronii_ and _A. media_ (0.80%), _A. lusitana_ and _A. popoffii_ (0.60%), _A. salmonicida_ (0.30%), _A.